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  • 1
    ISSN: 1420-9098
    Keywords: Stingless bees ; Plebeia remota ; social evolution ; division of labour
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The genusPlebeia has a special significance for the study of social evolution of stingless bees: morphologically primitive, its species display a wealth of behavioural evolution, especially with respect to the oviposition process. We comparePlebeia remota with the few other members of the genus studied so far. Related to its subtropical geographical range, brood production is seasonal (there is no brood in the colony in colder months), and adult workers occur as summer and winter bees. The nest is in tree cavities, and the involucrum is absent or restricted to the winter period. Brood cells are arranged in horizontal combs, and new cells are built completely synchronously. Each series consists of up to 50 cells, their number being mainly dependent on colony size. Construction speed is remarkably constant, allowing 4–6 batches per 24 hours. Cell building and provisioning are activities of a small group of specialized workers. The oviposition cycle follows the classical subdivisions for stingless bees. During the patrolling phase a worker may “offer” a trophic egg in a most remarkable way: while retreating backward from the queen she bends the abdomen under thorax and head, and lays an egg on the comb. This egg is eaten by the queen or a worker. The provisioning, oviposition and operculation of all cells occur simultaneously, each cell is provisioned by 4–9 workers. Localization of a cell by the queen may be facilitated by its characteristic guard, which “defends” the cell against the approaching queen. The degree of synchronization within a batch is very high: the duration per cell lasts 420–950 sec, the batch of up till 50 cells needs only 557–1160 sec. Operculation is done by a worker that was not involved in the previous steps. Males are generally produced by the queen. Several male producing cycles per year occur. In orphan colonies laying workers give rise to males, and in queenright colonies workers may occasionally reproduce as well. Division of labour follows the general pattern for stingless bees; however, cell building and provisioning are activities of a specialized group of workers.
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  • 2
    ISSN: 1420-9098
    Keywords: Apis mellifera ; queen pheromone ; queen rearing ; monogyny ; Africanized
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Queen rearing is suppressed in honey bees (Apis mellifera L.) by pheromones, particularly the queen's mandibular gland pheromone. In this study we compared this pheromonally-based inhibition between temperate and tropically-evolved honey bees. Colonies of European and Africanized bees were exposed to synthetic queen mandibular gland pheromone (QMP) for ten days following removal of resident queens, and their queen rearing responses were examined. Queen rearing was suppressed similarly in both European and Africanized honey bees with the addition of synthetic QMP, indicating that QMP acts on workers of both races in a comparable fashion. QMP completely suppressed queen cell production for two days, but by day six, cells containing queen larvae were present in all treated colonies, indicating that other signals play a role in the suppression of queen rearing. In queenless control colonies not treated with QMP, Africanized bees reared 30% fewer queens than Europeans, possibly due to racial differences in response to feedback from developing queens and/or their cells. Queen development rate was faster in Africanized colonies, or they selected older larvae to initiate cells, as only 1 % of queen cells were unsealed after 10 days compared with 12% unsealed cells in European colonies.
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  • 3
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    Insectes sociaux 42 (1995), S. 123-127 
    ISSN: 1420-9098
    Keywords: Drone congregation area ; sexual behaviour ; chemical communication ; male competition ; Meliponinae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary This is a first behavioural description of a large non-nest associated drone congregation of the stingless beeMelipona favosa. The about 400 drones had originated from different nests. The males interacted aggressively. Several gynes arrived at the drone congregation area (DCA). Olfactory stimuli triggered specific behaviours of the males as well as of the gynes but matings were not observed at the DCA.
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  • 4
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    Insectes sociaux 42 (1995), S. 137-144 
    ISSN: 1420-9098
    Keywords: Stomodeal trophallaxis ; Ponerinae ; ergatoid male ; ergatoid queen ; Hypoponera
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The present paper describes for the first time that adult-to-adult trophallaxis exists in ponerine ants. Furthermore, it shows that the adult castes of the ponerine andHypoponera sp. have different habits of trophallaxis. Workers display a soliciting behavior toward queens, males and workers, but receive regurgitated food only from workers. The workers are forced to stop soliciting for regurgitated food by the “whipping behavior” of the queen. Callow queens solicit regurgitated food from workers and ergatoid males and receive it, while mature queens do not solicit regurgitation from workers. Ergatoid males receive regurgitated food from workers and regurgitate it to queens. Alate males show no trophallactic food exchange with workers and queens. Trophallactic behavior was never observed between males of either winged or ergatoid types.
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  • 5
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    Insectes sociaux 38 (1991), S. 171-188 
    ISSN: 1420-9098
    Keywords: Halictidae ; Lasioglossum ; colony dynamics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Proximate control of colony dynamics was studied in the primitively eusocial halictine beeLasioglossum (Dialictus) zephyrum using allozyme markers. The results indicate that workers produce on average 15% of the male brood (range=0–50%) in small laboratory colonies made up of unrelated, single-generation, uninseminated females. This proportion is not influenced by colony size, but is influenced by the relative size of the queen. Large queens are more successful in dominating their workers than are small queens, the queen being defined as the female that is the mother of most of the brood produced in the colony. Older and larger females tend to become queens. Thus, while small differences in age (up to 4 days) influence which female becomes a queen, her ability to control her workers is primarily influenced by her relative size. The proportion of reproduction that is co-opted by the queen is negatively correlated with colony reproductivity (the number of males/day/female). Colony reproductivity is also negatively correlated with the standard deviation in size among females.
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  • 6
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    Insectes sociaux 38 (1991), S. 195-204 
    ISSN: 1420-9098
    Keywords: Formicidae ; Tapinoma ; population biology ; Australia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Nests ofTapinoma minutum were collected and mapped from a wet sclerophyll forest in New South Wales during the spring, summer, and fall seasons. Queen number was variable, indicating the population is both facultatively polygynous and polydomous. Electrophoretic data from three polymorphic enzymes revealed that relatedness among workers conformed to the Hamiltonian expectation of 0.75. Colony boundaries were inferred from electrophoretic data synthesized with nest spatial locations. For this species colonies were composed of at most three nests; this simple pattern of polydomy suggests it has a recent origin in this population. The pattern of facultative polygyny may be linked to an apparent high rate of colony orphaning.
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  • 7
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    Insectes sociaux 38 (1991), S. 217-218 
    ISSN: 1420-9098
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
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  • 8
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    Insectes sociaux 38 (1991), S. 213-216 
    ISSN: 1420-9098
    Keywords: Ropalidia marginata ; Unmated queens ; Individual selection ; Evolution of sociality
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary In the primitively eusocial tropical waspRopalidia marginata, five out of eleven colonies studied had an unmated female as their queen. In two colonies this was the case despite the presence of another mated individual in the colony. We found no detectable differences between colonies with unmated queens and those with mated queens. We argue that in species such asR. marginata, where intracolony relatedness is expected to be low and where sociality is likely to be maintained because several individuals have opportunities for direct reproduction in the future, individual selection is likely to override “the good of the colony” and lead to such phenomena as that of unmated queens.
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  • 9
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    Insectes sociaux 38 (1991), S. 219-220 
    ISSN: 1420-9098
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
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  • 10
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    Insectes sociaux 38 (1991), S. 251-262 
    ISSN: 1420-9098
    Keywords: Isoptera ; Termitidae ; Macrotermitinae ; instar duration ; production ; biomass
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Production in mature termite nests consists of a seasonal brood of reproductives and a continuous turnover of steriles. The sterile population of the nest remained fairly constant, with no regular seasonal fluctuations. Growth rates of steriles were estimated by interrupting the input and following the “missing cohort”. Estimated mean values of standing crop biomass and annual production in a mature nest were used to calculate a production-to-biomass ratio. In conjunction with data on the density of nests in the field, the biomass and production per hectare were estimated.
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  • 11
    ISSN: 1420-9098
    Keywords: Soil-feeding termites ; tropical rainforest ; humic compounds ; structural stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A comparison was made of some physicochemical characteristics of epigeous termitaries (nest walls and surrounding horizons) of four species of soil-feeding termites living in tropical rainforests. Our aim was to determine whether these species affect the different compounds involved in the structural stability of soil in a similar manner. Our data support the general finding that the structural stability of soil is correlated with organic matter, cations and the relative proportion of mineral elements. Of these parameters, the content of organic matter is the most significant factor effecting the stability of termite building materials. Analysis of humic compound distribution revealed that fulvic and humic acids, owing to their electrochemical properties, are highly involved. Also, the organic matter in termitaries is more polymerized than that of humiferous control horizons, leading to FA/HA ratios close to 1. The stability of nest walls and topsoils differs between the species. Generally, the speciesNoditermes lamanianus, Thoracotermes macrothorax andCubitermes fungifaber build nests that are enriched with organic matter and exchangeable cations, resulting in high structural stability. In contrast, materials worked byCrenetermes albotarsalis are not enriched with organic matter or cations and do not differ in stability from the control soils. It is concluded that any generalization on the overall influence of soil-feeding termites on soil fertility might be misleading. Only species which enrich their materials with organic matter, especially stabilised humic acids, contribute to soil conservation and hence fertility. Once the termitary is dead, its organic matter is again available to the soil ecosystem.
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  • 12
    ISSN: 1420-9098
    Keywords: Honey bee ; Apis mellifera ; queen pheromone ; age effect ; olfactory behavior ; olfactometer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Behavioral responses of differently aged worker beesApis mellifera to a queen pheromonal extract were analysed. The bees were tested individually in a four-armed olfactometer, one arm being scented with the pheromonal extract. This extract was prepared from heads of 14–17-day-old unmated queens. Among the components of the blend, 470 μg 9-keto-2-(E)-decenoic acid, 200 μg 9-hydroxy-2-(E)-decenoic acid and 5 μgp-hydroxybenzoic acid methyl ester per queen equivalent were dosed. An age dependency in the worker bees' olfactory response to the components of the queen extract was shown, the strongest response occurring below the age of 5 days.
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  • 13
    ISSN: 1420-9098
    Keywords: Ontogeny ; Formicidae ; learning ; queen attractant cues ; queen recognition ; Cataglyphis cursor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The behaviour ofCataglyphis cursor workers towards queens at 15 days, one month or two months after worker emergence was tested. Workers reared entirely with their own maternal queen were tested with this queen or with an unfamiliar alien queen. Workers transferred within 48 h of emerging to a new definitive nest with an alien queen were tested with this queen or with the original maternal queen. The degree of attraction to each of these queens and the workers' behavioural repertoire were measured and analysed. The results showed the following: 1) The attractiveness of queens and the workers' queen recognition behaviour were linked. 2) Although unfamiliar alien queens hardly attract workers, familiar alien queens were as attractive as maternal queens, and induced the same strongly marked and unique worker response, indicating that workers learn queen attractant cues in the days immediately after emergence. 3) Agonistic reactions were observed, but workers continued to be attracted to their maternal queen even after developing an attraction response to an alien queen with which they had been reared. These results agree with the proposal that queens produce two kinds of pheromones, those that attract workers and those that mediate recognition of queens by workers. These results show the ability of workers to discriminate between queens. Workers are attracted to any queen, but recognize as nestmates only maternal or alien queens with which they have been maintained. 4) The differential in worker attraction and recognition from 15 days to 2 months and its modifications by post-imaginal experience illustrate worker behavioural ontogeny, which is a basis of social discrimination.
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  • 14
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    Insectes sociaux 38 (1991), S. 307-316 
    ISSN: 1420-9098
    Keywords: Dolichoderus ; silk production ; worker ; nest building ; rain forest ; Malaysia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary In a montane Malayan rain forest, at an elevation of about 900 m above sea level, we found an undetermined and possibly undescribedDolichoderus species of thethoracicus group, living in colonies consisting of 50–100 silken pavilions on the undersides of leaves of different species of trees. Inside these pavilions, the ants kept scale insects, which we never found outside the nests on the colony tree. The stock of symbionts was actively regulated; supernumerary scale insects were thrown to the ground by the workers. New pavilions were colonized with scale insects. Our observations and behavioural experiments revealed that the silken material is produced by neither the brood nor the scale insects, but by the worker ants. This is the first proof of weaver ants outside the subfamily Camponotinae.
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  • 15
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    Insectes sociaux 38 (1991), S. 333-334 
    ISSN: 1420-9098
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
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  • 16
    ISSN: 1420-9098
    Keywords: Thaumatomyrmex ; taxonomy ; comparative morphology ; predation ; Polyxenidae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We describe, for the first time, the predatory behaviour ofThaumatomyrmex ants on millipedes of the family Polyxenidae, based on field observations ofT. atrox and a field and laboratory study ofT. contumax. The capture of the prey and the removal process of its body-covering setae by the ants before they eat the millipede are described. This specialized behaviour in at least two species of the genus, belonging to two distinct groups of species, indicates a general trend inThaumatomyrmex. We coupled this study with a comparative morphological analysis of the mouthparts and digestive tube of these and otherThaumatomyrmex species. Also, we report the first case of sympatry in the genus, which suggests thatThaumatomyrmex includes several species, and not only one highly variable taxon, as hypothetized earlier.
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  • 17
    ISSN: 1420-9098
    Keywords: Soldier ; social behaviour ; aphid ; Pseudoregma
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Life history and behavioural characteristics of the bamboo aphid,Pseudoregma bambucicola (Takahashi), which has sterile soldiers, were studied in the laboratory. The stadium of normal (fertile) first instar larvae was two times longer than that of second instar larvae, and the stadium of soldier-type (sterile) first instar larvae was much longer (max. 116 days) than the stadium of normal first instar, suggesting that soldiers are able to take nutrition from bamboo. Stimulation of larvae with breath, vibration of bamboo shoots or disturbing the larvae with the tip of a fine brush induced significantly more defensive acts by soldiers than those by normal larvae — the latter usually fled. Soldiers did not attack non-kin conspecific intruders or even aphids of different species, suggesting that, in this species, kin-recognition ability is low.
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  • 18
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    Insectes sociaux 38 (1991), S. 331-332 
    ISSN: 1420-9098
    Source: Springer Online Journal Archives 1860-2000
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  • 19
    ISSN: 1420-9098
    Keywords: Nuptial flights ; sexual behaviour ; polygyny ; Leptothoracini
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We describe in detail a very large nuptial flight of the antLeptothorax acervorum at an open hilltop site in Britain. The mating behaviour of these ants involved not only a large mating swarm but also sexual/calling behaviour by the females. The females left the flight to land on vertical objects, where they took up a characteristic calling posture, in which females of closely related species are known to release pheromones that are sexually attractive to males. ThatLeptothorax acervorum has a complex mating behaviour involving both large nuptial flights and sexual calling has important consequences for the interpretation of the evolution of polygyny in this species and social parasitism in its close relatives.
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  • 20
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    Insectes sociaux 38 (1991), S. 345-349 
    ISSN: 1420-9098
    Keywords: Chemical communication ; exploration ; Lasius pallitarsis ; novelty ; recruitment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Lasius pallitarsis ants were placed in situations where they encountered unfamiliar areas and had to choose between one of two directions for further exploration. Workers advancing onto new ground apparently leave behind some chemical signature to which later ants orient. This orientation occurred under two types of experimental conditions. First, ants show a significant tendency to follow each other as they advance out from their colony into unexplored areas. The same ants transferred into an entirely novel situation, in which there is no obvious “homeward” direction, show similar behavior. When ants are coming from familiar ground, following tends to increase as the number of ants passing the decision point increases. However, following decreases when ants are on entirely novel ground. The results are discussed in relation to models describing foraging responses.
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  • 21
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    Insectes sociaux 38 (1991), S. 351-363 
    ISSN: 1420-9098
    Keywords: Central Spain ; cereal croplands ; density ; distribution ; Messor ; nests ; site selection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Patterns of abundance and site selection of granivorous ant nests were investigated in extensive cereal croplands of Central Spain. Nest densities and distributions were measured in two consecutive summers (1988 and 1989), together with habitat physiognomy and seed availability. Nest site selection patterns were analysed at two spatial scales (landscape and microhabitat) with respect to habitat physiognomy. Results indicate a very constant and predictable pattern of both nest abundance and nest site selection. Granivorous ant nests were most abundant in shrublands, and shrubby microsites were selected for nest placement. Croplands, and microsites with high covers of bare ground and litter, were avoided. These patterns were consistent between years despite a 1.7-fold increase in shrubland nest densities, that was attributed to the exceptionally dry winter between nest censuses. I suggest that winter survivorship of ant nests in the unploughed landscape units, and periodic ploughing in croplands, may be the main factors constraining granivorous ant densities in the landscape studied.
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  • 22
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    Insectes sociaux 38 (1991), S. 423-437 
    ISSN: 1420-9098
    Keywords: Stenogastrinae ; Anischnogaster ; social behaviour ; colony biology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Level of social organization, adult behaviour, size and development of the brood in three species ofAnischnogaster are described. The normal colony size in all the three species was one female per nest, and colony size never exceeded two females per nest. The social interactions, which were only observed in one species, did not include any marked dominance behaviour, but there was clear caste differentiation, with the older female guarding the nest while the younger female foraged for food. InAnischnogaster sp. A only some eggs and larvae have abdominal secretion, while no secretion at all was found on the eggs and larvae ofA. laticeps. In spite of this, the Dufour's gland was found to be well developed. The significance of this is discussed. Females ofA. laticeps were found to fall into two groups distinguished by the length of the sting. The larvae seem quite similar to those of other Stenogastrinae and have, apparently, only four instars.
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  • 23
    ISSN: 1420-9098
    Keywords: Tropical soils ; porosity ; Isoptera
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Description / Table of Contents: Summary Insights on the porous properties and evolving sizes of sample pores have been derived by means of physical measures carried out on several soil samples of various sizes placed under a hydric strain of 0.1 MPa. Under the very influence ofT. macrothorax (humivorous termite), surface horizons are the first to be altered. Within one metre's radius around their nest, a significant increase of porosity is noticeable, reaching an exceptionally high degree at the bottom of the nest. The volume of pores 〉 1.5 μm is held to be considerably amplified as compared with control soils; however, the interference 〈 1.5 μm pores. The masticative and mechanical power of termites on the soil, together with the organic matter bulk increase turn out to play a paramount role in the stability ofT. macrothorax constructions. On the contrary, horizons in the vicinity ofM. mulleri's nests (fungus growing termite) undergo a diminutive porosity with the total disappearance of pores 〉 1.5 μm. A sharp decrease or organic matter rates has been recorded. Alternatively, as far asM. mulleri are concerned, physical and physico-chemical data do emphasize that the soil structural stability is not to be correctly ensured by the cohesive properties which are normally to be taken into account with this type of material.
    Notes: Résumé A partir de mesures physiques réalisées sur des échantillons de sols de différentes tailles portés a une contrainte hydrique de 0,1 MPa on obtient des informations sur la porosite et l'évolution de la taille des pores des échantillons. L'action deT. macrothorax (termite humivore) sur le sol affecte en premier lieu les horizons de surface. On note, à 1 mètre autour du nid, une forte augmentation de la porosité qui devient exceptionnellement élevée au pied de la termitière. Le volume des pores de 〉 à 1,5 μm est considérablement amplifié par rapport au sol témoin mais la contribution des pores de 〈 à 1,5 μm diminue. L'action mécanique de mastication du sol par les termites conjuguée à l'augmentation de matière organique apparait jouer un rôle décisif dans la stabilité des contructions deT. macrothorax. Les horizons avoisinants le nid deM. mülleri (termite champignonniste) ainsi que la muraille du nid enregistrent une diminution de la porosité avec disparition complète des pores 〉 1,5 μm. On constate dans ce cas une baisse du taux de matière organique dans les échantillons. Dans le cas deM. mülleri les données physiques et physico-chimiques montrent que la stabilité structurale du sol ne peut être vraisemblablement pas assurée par les forces de cohésion envisagées habituellement dans ce genre de matériau.
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  • 24
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    Insectes sociaux 39 (1992), S. 1-1 
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  • 25
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    Insectes sociaux 39 (1992), S. 3-13 
    ISSN: 1420-9098
    Keywords: Ants ; colony founding ; competition ; Lasius pallitarsis ; pleometrosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Ant queens often cooperate in starting colonies (pleometrosis), but not all foundresses are likely to achieve equal reproductive success. Therefore, joining decisions may be influenced by queens' perceptions of a partner's likelihood to be of mutualistic benefit or to be a successful competitor in eventually controlling reproduction. Large queen size (as measured by weight) was assumed to be a desired characteristic in a mutualistic partner, but to be avoided in a potential competitor. With respect to this variable,Lasius pallitarsis queens appeared to join others in a manner consistent with increasing their competitive advantage. When given a choice between joining another queen or nesting alone, only queens with a large weight advantage were significantly likely to join. When given a choice between joining either a light or a heavy queen, queens of all weights preferentially joined the lighter resident. Moreover, when queen condition was improved by feeding, changes in joining behavior were consistent with predictions of improved competitive ability. Finally, lighter queens were more likely to leave nest sites when joined by others. However, queens significantly aggregated when in high densities, which may be consistent with gaining mutualistic benefits. Pleometrosis appears to have an evolutionary dynamic between mutualistic group benefits and individual competition to monopolize those benefits.
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  • 26
    ISSN: 1420-9098
    Keywords: Ants ; polygyny ; polydomy ; sibling species
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The speciesFormica aquilonia andF. lugubris of the mound-building red wood ants have a disjunct boreoalpine distribution in Europe. The populations ofF. aquilonia in Finland, Switzerland and the British Isles show little genetic differentiation, whereas the populations ofF. lugubris show considerable differentiation. The Central European populations morphologically identified asF. lugubris can be genetically divided into two groups (here called types A and B). Type B is found in the Alps and the Jura mountains, and is genetically inseparable fromF. aquilonia. Type A lives sympatrically with type B in the Jura mountains and is also found in the British Isles. Sympatry of the two types in the Jura shows that these are separate species. It remains open whether type B is morphologically atypicalF. aquilonia or whether it is a separate species, perhaps with a past history of introgression betweenF. aquilonia andF. lugubris. The gene frequencies in the Finnish populations ofF. lugubris differ from those of both types A and B. Genetic differences withinF. lugubris indicate that the populations have evolved separately for a long time. The social structure ofF. lugubris colonies also shows geographic variation. The nests in Finland and the British Isles seem to be mainly monogynous and monodomous, whereas the nests in Central Europe are polygynous and form polydomous colonies.F. aquilonia has polygynous and polydomous colonies in all populations studied.
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  • 27
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    Insectes sociaux 39 (1992), S. 117-127 
    ISSN: 1420-9098
    Keywords: Competition ; community ; Leptothorax ; Monomorium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Interference competition for nest sites was studied in ant communities dominated byLeptothorax congruus in the suburbs of Tokyo, central Japan. At the two study plots located in a deciduous wood and in grassland,L. congruus constructed nests in dead branches or stems of dead grasses. Approximately 50% of the nests were physically broken within a year, suggesting that they were very fragile. Of totals of 67 and 91 nests ofL. congruus marked at the two sites, 12 (17.5%) and 53 (58.2%) nests, respectively, were replaced by other ant species (Monomorium intrudens,Crematogaster brunnea teranishii,Camponotus itoi andLasius sp.) which were common in both habitats. Field observation suggested that, among these ants,M. intrudens was a major competitor usurping the nests ofL. congruus by aggressive invasion.
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  • 28
    ISSN: 1420-9098
    Keywords: Ants ; colony growth ; development of behavior ; predation strategy ; guarding behavior
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We traced the development in the laboratory of 18 young colonies of the arboricolous ponerine antEctatomma tuberculatum. Colony foundation is of the partially-claustral type. During the early stages, when the colony is entirely dependent on the queen's behavior, the growth of the colony in terms of number of workers produced over time was relatively predictable. Afterwards, divergence in colony growth in function of the time increases as fast as the number of workers influences the efficiency of colony provisioning. Comparative analysis indicated clear changes in the predation behavior of foundresses and workers as colonies developed. For any stage of colony growth, all individuals provisioned the nest with dead prey or sugar-rich substances in the same way. However, prey hunting involves two different strategies. Foundresses and nanitic workers (originating from colonies with 9–15 workers) foraged actively, catching prey as the result of random encounters. Post-nanitic foragers (originating from colonies with 20–30 workers) and those from nature colonies developed an ambush strategy. Workers in these colonies gained experience at catching and handling prey during a period when they acted as nest guards, and so tended to be more efficient hunters than poorly experienced foundresses or nanitic foragers. The change in strategy was also positively correlated with an increase in the size of workers as the colony matured. A stable maximum in workers size is apparently reached only after the appearance of efficiently hunting foragers, presumably in numbers sufficient to provide adequate quantity and quality of larval food. Such a correlation between worker size and colony growth, assumed general for all ants, has not been demonstrated for Ponerinae before this work.
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  • 29
    ISSN: 1420-9098
    Keywords: African honey bee ; scutellata ; swarming ; absconding ; migration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The relationship between the annual colony cycle and seasonal patterns of forage availability was investigated for the African honey bee,Apis mellifera scutellata, in the Okavango River Delta, Botswana. The annual cycle occurred in three distinct periods. The swarming season occurred from October-November, following two to three months of intense brood production, and coincided with the end of peak forage abundance. The migration season occurred from November-May and coincided with reduced and variable floral resources. During the migration season, brood production and food storage were generally low but quite variable from month to month, and swarms passing over the study area at this time traveled in an easterly direction. The migration season was followed by the establishment period (June-September), in which large numbers of new colonies traveling from the west moved into the study area. The establishment period coincided with, and slightly preceded, the period of peak forage abundance, and colonies devoted resources collected at this time almost entirely to brood rearing, which culminated in swarm production. The data suggest that honey bee colonies in the Okavango are mobile and gear their reproduction and movement to seasonally shifting resource pattern.
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  • 30
    ISSN: 1420-9098
    Keywords: Apis mellifera scutellata ; African honey bee ; foraging ; brood rearing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Seasonal foraging patterns were investigated using six observation colonies maintained in the Okavango Delta, Botswana. Pollen collection, flight from the hive, and recruitment for pollen and nectar sources occurred throughout the 11 months of the study. However, the distribution of foraging activity throughout the day changed seasonally. Colonies emphasized recruitment for pollen sites throughout most of the year. Brood production occurred in all months except May, and there was a significant, positive correlation between the proportion of recruitment activity devoted to pollen sources and the amount of brood comb in the colonies. The seasonal foraging patterns ofscutellata in the Okavango were similar to those of Africanized honey bees in the neotropics. The extended foraging season and emphasis on pollen collection may be associated with the high swarming rates and migrational movements of tropical honey bees.
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  • 31
    ISSN: 1420-9098
    Keywords: Camponotus pennsylvanicus ; compound eye ; ommatidia number ; Polymorphism ; caste development
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The relation of worker size to ommatidia number was examined in the polymorphic antCamponotus pennsylvanicus (DeGeer). Linear regression described this relationship as:Y = 260.9 + 113.6×; whereYis ommatidia number andX is head width. A log-log regression described this relationship as:Y = 323.5 + 286.9*logX(r 2 = 0.98). This analysis indicated an allometric relation of ommatidia number to head width, where ommatidia numbers increase at a slower rate than head width. This relationship is discussed in terms of ethotypes associated with worker morphotypes, and the possible mechanisms regulating polymorphic development.
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  • 32
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    Insectes sociaux 39 (1992), S. 201-213 
    ISSN: 1420-9098
    Keywords: Foraging ; recruitment ; colonies ; social insects ; ants
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A numerical model of an eusocial colony foraging for food showed that, for each set of values of resource density, resource size and recruitment system employed, a given optimal proportion of scouts in the colony maximize the amount of resources retrieved by a colony during a fixed period. The model predicts that ants using mass recruitment systems should have larger colonies with small foragers, and should forage on large food sources. Retrieval of small food sources by small colonies is best achieved with large workers using individual foraging strategies. For mass foragers, several food sources are best retrieved using democratic decision-making systems in recruitment, whereas for very large food sources at very low mean food patch density, autocratic decision-making systems are optimal. Some of the experimental evidence available is discussed in the light of these findings, as they confirm the prediction that large colonies with small workers have mass recruitment systems, whereas workers of small colonies with large workers are generally lone foragers.
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  • 33
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    Insectes sociaux 43 (1996), S. 47-51 
    ISSN: 1420-9098
    Keywords: Colony foundation ; haplometrosis ; pleometrosis ; Acromyrmex striatus ; Attini
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Laboratory tests with mated females of the leaf-cutting antsAcromyrmex striatus (Myrmicinae, Attini) were conducted to determine if the colony foundation is a solitary or a mutualistic process. We have also tested the effect of foundresses density and number of available areas in this process. Three bioassays were performed: with single foundresses; with paired foundresses; and with groups of 8 to 18 foundresses. The results suggest that the foundation can be by haplometrosis or pleometrosis, possibly depending on physical distances between or densities of foundresses. Foraging activity was common in haplometrotic queens and in foundress pairs, but no foraging occurred in groups of foundresses.
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  • 34
    ISSN: 1420-9098
    Keywords: Interspecific trail following ; workerless inquiline ant ; Pogonomyrmex colei ; reproductive biology ; seed-harvester ants
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Pogonomyrmex colei is a workerless inquiline ant known only from nests ofP. rugosus, its closest relative. Ten of 776 (1.3%) host nests were parasitized at a site in central Arizona, while none of 1499 potential host colonies were parasitized at two other locales. Colonies ofP. colei are perennial, and host alate females in 9 of 10 colonies demonstrates that host queens survive parasitism. Three of 10 colonies died over 19 colony years of observation, while only 1 of 601 colonies became newly parasitized. Mating occurs in morning for up to 2–3 days following summer and fall rains and in afternoon during cool fall days. Mating is intranidal just outside the nest entrance, with males returning to the natal nest. MaleP. colei may be flightless because their wing area is reduced compared to host males. Females fly from the nest and locate potential host colonies by following trunk trails. Workers are the largest barrier to nest establishment, as they removed over 90% ofP. colei females placed in trunk trails or that entered host nests. Males and females ofP. colei andP. anergismus, the only other congeneric inquiline species, are diminutive compared to their hosts, with females 30% lighter than host workers. Fat content is lower and water content is higher inP. colei andP. anergismus females than in their hosts.
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  • 35
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    Insectes sociaux 43 (1996), S. 101-104 
    ISSN: 1420-9098
    Keywords: Cataglyphis floricola ; diet ; food resources ; petal consumption
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary C. floricola is an endemic species from the southern Iberian Peninsula which collects large amounts ofHalimium halimifolium petals. Laboratory and field observations confirm that both workers and larvae feed on these petals, which represent an important food resource forC. floricola colonies. This petal consumption is a very unusual ant diet.
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  • 36
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    Insectes sociaux 43 (1996), S. 111-118 
    ISSN: 1420-9098
    Keywords: Predation ; polyethism ; food exchange ; behavioral flexibility ; Ectatomma ruidum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary During laboratory experiments, two categories of prey-foraging workers were found inEctatomma ruidum: stingers and transporters. When numerous live drosophila were offered to the ants, one group of hunters specialized in killing the prey and another in transporting simultaneously the dead drosophila to the nest. Sometimes, there was a transfer of prey by a stinger towards a transporter, after an active soliciting of the transporter by antennation or by using the forelegs. We found high positive correlations between the colony size and the number of ants in each subcaste. A negative correlation existed between the colony size and the proportion of hunters. However, the proportion of workers in the two behavioral subcastes of hunters was stable in spite of differences in colony size. The phylogenetic interest of this type of cooperative predation is discussed.
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  • 37
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    Insectes sociaux 46 (1999), S. 131-136 
    ISSN: 1420-9098
    Keywords: Key words:Vespula, Polistes, Vespidae, foraging, resource choice.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary: The role of visual cues provided by resident wasps on resource choice by yellowjacket and paper wasp foragers was investigated. Large spring queen yellowjackets and small early season yellowjacket foragers (Vespula germanica, Vespula maculifrons, and Vespula vidua) were extracted in hexane to remove odors and posed as though feeding at petri dish feeders bearing daisy-like flower models, equipped with microcapillary feeding tubes, and containing 1:3 honey:water solution. An array of five feeders was presented to foragers at a suburban and a woodland site in Saratoga Springs, New York. The visual cues provided by resident wasps influenced resource choice by approaching social wasp foragers. Vespula germanica, an introduced yellowjacket species that tends to dominate at rich resources, was the only wasp visiting the suburban feeders. Foragers of this species preferentially fed on feeders and flowers with posed wasps and fed most often next to large wasps. Polistes fuscatus foragers at the woodland site similarly preferred to feed on occupied feeders and flowers. Vespula maculifrons and V. consobrina preferentially visited unoccupied feeders. Individual V. maculifrons, V. consobrina and V. vidua foragers that landed on occupied feeders all preferentially visited unoccupied flowers on those feeders. Vespula vidua and V. flavopilosa foragers did not demonstrate a feeder preference based on the presence/absence of posed wasps. Vespula consobrina foragers that visited occupied feeders preferred those occupied by extracted V. maculifrons queens and workers; no other wasps showed species based landing preferences.
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  • 38
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    Insectes sociaux 46 (1999), S. 137-145 
    ISSN: 1420-9098
    Keywords: Key words: Mating frequency, polyandry, Apis mellifera sicula, honey bees, microsatellite.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary: Honey bee queens have been shown to mate with a high number of males, but the evolutionary advantage of this high degree of polyandry is still unclear. Mating data from a number of different Apis species and subspecies are needed to help explain polyandry in honey bees. Pupae of four colonies of Apis mellifera sicula from Sicily were genotyped on three polymorphic microsatellite loci. The genotypes of the queens and fathering drones from these colonies were deduced from the genotypes of the pupae. We found no evidence for polygyny, at least we can exclude more than one functional queen, even super-sister queens, if maternity contributions are equal. The four queens mated with at least 5 to 12 (mean: 9.3 ± 3.0 SE) drones. We estimate the error in our determination of the mating frequency that is caused by limited genetic resolution of the marker loci to be less than 1 mating given that Hardy-Weinberg assumptions are satisfied. However, the drones the single queens mated with may be a non-random sample of the whole population, so that detection error may be more severe. The average pedigree relatedness among workers within the colonies was estimated to be 0.341. These results are within the range of those found in other A. mellifera subspecies and Apis species except A. dorsata. We speculate that mating frequency may be positively correlated with drone density.
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  • 39
    ISSN: 1420-9098
    Keywords: Oecophylla longinoda ; orientation ; trail pheromones ; fæcal marking ; chemical communication ; tropics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Trail communication of the weaver antOecophylla longinoda is highly adapted to the African rain forests, insofar natural selection in the tropics might favour chemical trails which are durable in nature. A dry chemical trail can last over nine weeks, and over ten months when reinforced with fecal marking. The trail pheromones are resistant to rain, whether they are fresh or three months old, and whether they are reinforced or not with anal deposits.
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  • 40
    ISSN: 1420-9098
    Keywords: Myrmica rubra ; isozymes ; isoelectric focusing
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    Topics: Biology
    Notes: Summary A polymorphism in the enzyme malate dehydrogenase in Dorset populations ofMyrmica rubra was detected using isoelectric focusing (IEF). The polymorphism was not detected on native polyacrylamide gels. Two forms, with pI values of 4.9 and 5.7, were resolved. Several lines of evidence show that the polymorphism has an environmental rather than a genetic basis. The cause of the change from one phenotype to the other may be related to a seasonally varying factor. The results indicate that whilst IEF has great potential for revealing isozyme polymorphisms in ants, care should be taken in interpreting results.
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  • 41
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    Insectes sociaux 39 (1992), S. 451-454 
    ISSN: 1420-9098
    Keywords: Foraging ; reliability ; task performance ; wasps
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    Topics: Biology
    Notes: Summary Foragers of the neotropical swarm-founding waspPolybia occidentalis showed improved task performance, as indicated by foraging success rate, with foraging age. Foragers also spent significantly more time in the field on foraging trips as they aged, while foraging rate did not change with age. These patterns were not explained by directional changes in resource availability or colony need over time. We compare these results to earlier findings on changes in task performance with experience in social insect foragers, and suggest that increases in forager persistence in the field explain improved foraging success with experience.
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  • 42
    ISSN: 1420-9098
    Keywords: Key words: Worker polymorphism, ant-plant interaction, mutualism, morphometrics.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary: We compared intranidal variation in worker size in the two closely related plant-ants Aphomomyrmex afer and Petalomyrmex phylax. Each of these genera is monotypic, and the two appear to be sister species among extant ants. Workers of A. afer are larger on average and exhibit much greater intranidal size variation. Workers of P. phylax are smaller and much less variable in size. Both species show weak allometry for some pairs of characters. Head shape is also different in workers of the two species. We discuss these differences in relation to the ecology of A. afer and P. phylax, and propose a scenario for the evolutionary divergence of worker morphology in these two species. Based on comparisons of these two monotypic genera with related ants, we suggest that reduced intranidal variation in worker size is a derived trait in Petalomyrmex.
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  • 43
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    Insectes sociaux 46 (1999), S. 208-218 
    ISSN: 1420-9098
    Keywords: Key words:Melipona panamica, stingless bees, Apidae, nestmate recognition, worker oviposition.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary: Nestmate recognition was studied in the Neotropical stingless bee Melipona panamica, a species in which workers “sneak” their own reproductive eggs into 1 % of brood cells. We manipulated four factors that could influence individual recognition cues: the mother queen, the environment during the immature stage, the environment during the early adult stage, and worker age. We also simulated the action of natural enemies on colonies tested for discrimination of such worker characteristics. All factors that we tested affected responses of the discriminating workers, which could recognize sisters, nieces and unrelated workers. Previous exposure of unrelated callow bees to the odor of the host nest greatly increased chances of acceptance by the host colony. Probability of acceptance decreased, however, with increasing age of introduced bees or increasing disturbance of the host colony. These complexities in patterns of nestmate recognition and nest defense are adequately explained from the standpoint of inclusive fitness of the discriminating workers. Differences in nestmate recognition and worker egg laying among Meliponini are also discussed.
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  • 44
    ISSN: 1420-9098
    Keywords: Key words: Mitochondrial DNA, restriction site polymorphism, meat ants, Iridomyrmex purpureus, polygyny.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary: The Australian meat ant Iridomyrmex purpureus is known from observations and allozyme surveys to have a high proportion of mature colonies polygynous, but very few incipient ones. Sixteen colonies in the vicinity of Maryborough, Victoria, revealed four mtDNA restriction site haplotypes. One of these nests presented two different haplotypes; given the haplotype frequencies, this result suggests that a high proportion of mature nests contain unrelated queens.
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  • 45
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    Insectes sociaux 44 (1997), S. 15-21 
    ISSN: 1420-9098
    Keywords: Key words: Mangrove, ants, Polyrhachis sokolova, nest, inundation, foraging.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary: The nest sites of the mud-nesting ant Polyrhachis sokolova were studied in Darwin Harbour mangroves. They were found from the Ceriops tagal zone to the Rhizophora stylosa zone at elevations ranging from 7.22 to 5.99 meters above the lowest astronomical tide (LAT), which means that the nests were inundated in 13‐61% of all high tides and for durations of up to 3.5 hours. The nest structure was studied by excavating nests and making a cast of the galleries using polyurethane foam. The nests were quite extensive, normally with two elevated nest entrances and galleries down to depths of 45 cm. The loose soil particles at the nest entrances collapsed when the tide reached them and formed a stopper which prevented water from intruding into the nest. In this way, the galleries remained dry during high tide. The ants showed a clear swimming or "walking on the surface" behaviour when they returned to the nest just before the entrance collapsed and during ebb. The tolerance of the ants to submergence was tested in the laboratory, with 50% mortality after 11 hours submergence in seawater at 23 °C, and only 3.5 hours in water at 33 °C. Therefore, the nesting behaviour with trapped air in the galleries is necessary for survival in these environments.
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  • 46
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    Insectes sociaux 44 (1997), S. 23-33 
    ISSN: 1420-9098
    Keywords: Key words: Diversity, chaparral, Formicidae, inventory methods, serpentine.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary: In northern California, ant assemblages in 8 sites in serpentine chaparral habitat were compared with those occurring in 8 chaparral sites on adjacent non-serpentine soils. A total of 27 species of ants was found: 22 species were collected in non-serpentine chaparral and 20 species in serpentine chaparral. Seven species were collected exclusively in non-serpentine, and 5 species were found only in serpentine habitats. A Formica species, conspecific with or closely related to F. xerophila, was found only in serpentine chaparral. Subsequent collections suggest that in northern California, this species is confined to serpentine outcrops. Two other species significantly differed in frequency of occurrence in each habit:Camponotus hyatti, C. cf. vicinus. Five species showed marginal significant differences in their relative abundance between habitats:Camponotus hyatti, C. cf. vicinus, Formica moki, Prenolepis imparis, Leptothorax nevadensis, Stenamma diecki.
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  • 47
    ISSN: 1420-9098
    Keywords: Key words: Foraging activity, Meliponinae, Melipona favosa, M. fasciata, M. beecheii, Tetragonisca angustula.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary: For Melipona fasciata, M. beecheii, M. favosa and Tetragonisca angustula we found distinct intergeneric differences in foraging activity patterns. The Melipona species had a longer daily foraging activity period than T. angustula. Pollen foraging patterns of the Melipona species were different from that of T. angustula: Melipona collect pollen earlier in the day. In an experimental habitat without competitors, Melipona favosa did not collect pollen very early in the day. ¶Individually marked returning foragers demonstrated in the course of the day distinct differences in nature and frequency of interactions with nest mates. Individual foraging flight frequency was lower and the intranidal transfer of nectar was delayed when syrup of a lower concentration was offered. ¶The regulation of daily foraging activity patterns and the nectar foraging behaviour of individual worker bees are discussed.
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  • 48
    ISSN: 1420-9098
    Keywords: Key words: Termites, nest construction, plant growth suppression, plant abundance.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary: Termites invest considerable time and energy constructing elaborate mounds out of clay, sand, silt, excreta and saliva, which they defend vigorously against predators and parasites. Termite mounds are fertile and potentially attractive resources for plants, which may threaten the stability of the mound. Field surveys at Boola Boola Forest in SE Australia revealed significantly higher abundance and diversity of vascular plants growing on uninhabited than inhabited mounds of the termite Coptotermes lacteus. These data reveal that the presence of termites affects the establishment and growth of vegetation. Germination experiments indicate that plant growth suppression is not chemically mediated but rather is due to the impenetrable nature of the mound surface. Analyses of soil types suggests that termite workers may choose particular clay minerals for mound construction, which enhances surface impenetrability and thus increases the engineered integrity of the mound.
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  • 49
    ISSN: 1420-9098
    Keywords: Key words: Eusocial aphids, Pseudoregma bambucicola, resource allocation, soldier investment, reproductive schedule.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary: The reproductive characteristics of the soldier-producing aphid Pseudoregma bambucicola were studied in Kagoshima, Southern Japan, to know the factors affecting soldier production of eusocial aphids. The soldier proportion in aphid colonies was highest from October to November. In some large colonies, soldiers were observed in all seasons except in July when colony size was relatively small. Multiple regression analysis showed that the colony size was a principal factor affecting soldier proportion throughout a year. Other social or environmental factors such as aphid composition, host plant conditions and predator abundance were not always significant. Rearing experiments revealed that large colonies (≥1,000 individuals) produced soldiers in almost all seasons while small colonies (〈1,000) never produced any soldiers. The caste-production schedule of adult females was examined in the field. When solitary females produced both castes, they usually produced normal nymphs first and then soldiers. Females from large colonies tended to produce more soldiers in the earlier period of their lifetime, whereas females from newly established small colonies produced no or only a few soldiers at later times. The average number of soldiers and normal nymphs produced consecutively by a single female was 〉10 and 〉20, respectively. Because they have a small number of ovarioles (〈15 on average), females should alter caste production within the same ovarioles according to changes in environmental conditions. Artificial removal or introduction of predators and reduction of colony size did not affect soldier production over two successive generations, revealing maternal effects on soldier production. Females cannot shift caste production quickly in response to changes in predator abundance and colony size. This is probably due to early developmental determination of castes within the mother's body.
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  • 50
    ISSN: 1420-9098
    Keywords: Key words: Leptothorax, colony size, demography, polydomy, Formicidae.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary: 484 nests of Leptothorax tuberointerruptus were collected from a coastal limestone grassland community in Dorset, England, over a 16 month period from February 1992 to May 1993. Behavioural observations and dissections of females strongly suggested that the nests were obligately monogynous. Electrophoretic data also suggested that within most nests all the workers shared the same mother and father. Counts of nest contents revealed temporary but dramatic drops in both worker and queen numbers per nest in May—June 1992. Seasonal polydomy is postulated to be the cause of this variation. Such dramatic variation highlights the importance of sampling over as much space and time as possible if premature conclusions about colony demography are to be avoided.
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  • 51
    ISSN: 1420-9098
    Keywords: Key words: Ants, foraging, interspecific competition, Myrmica sabuleti, Formica fusca.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary: Myrmica sabuleti forms mature colonies of about one thousand workers and a few queens. Although living in dry and sunny biotopes, this species avoids foraging during the warmer hours of the day which correspond to the period of the maximum foraging activity of two sympatric species, Formica fusca and F. cunicularia. M. sabuleti is the most frequently observed species on the extrafloral nectaries of Vicia sativa, even during the warmer hours of the day, whereas F. fusca is the most frequent species during those hours at tubes of 1M sucrose solutions placed on the ground. In spite of this temporal segregation, the foraging activity of M. sabuleti and F. fusca overlaps two times a day (10:00‐11:00 am and 5:00‐8:00 pm). Newly discovered large food sources are exploited by M. sabuleti through an explosively increasing recruitment, whereas workers of F. fusca forage mainly individually. Interference between M. sabuleti and F. fusca was studied when offering sucrose solutions, large dead insects unretrievable by individual foragers of either species (cockroaches), medium-sized insects retrievable by single foragers of F. fusca but not by single M. sabuleti(larvae of Calliphora erythrocephala) and small insects (Drosophila) retrievable by individual foragers of both species. Owing to its rapid recruitment, M. sabuleti is able to displace F. fusca from sucrose solution and large dead prey during the overlaping of the activity cycles of both species. When medium-sized corpses are offered, the issue depends on the speed of the events. F. fusca is able to take the prey away only if it discovers it before M. sabuleti has recruited nestmates. Small dead prey do not lead to interference, but is taken by the first worker that finds it.
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  • 52
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    Insectes sociaux 41 (1994), S. 99-110 
    ISSN: 1420-9098
    Keywords: Nesting biology ; nest re-use ; Eulaema nigrita ; Euglossini ; Apidae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The nesting behavior of the euglossine beeEulaema nigrita was observed in the laboratory after being transferred from three nests to observation boxes. Nests were re-used by successive generations with more than one female working in each re-use process. Associated females were always of the same generation. All females that shared a nest foraged for construction materials (mud, excrement and resin) and each constructed, provisioned and oviposited in her own cells. The number of cells constructed by each female ranged from one to 23. Females stayed in the nests for periods ranging from 15 to 59 days during the hot and wet season and from five to 78 days during the cool and dry season. The egg-to-adult period was related to climatic conditions, and in all re-use processes it was longer than the time of residence of the females in the nests. The meloid beetleMeloetyphlus attacephalus was the only nest parasite. Due to the attack method employed by this parasite, the presence of more than one female in the nest did not result in improved nest defense.
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  • 53
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    Insectes sociaux 41 (1994), S. 301-307 
    ISSN: 1420-9098
    Keywords: Bombus terrestris ; bumble bees ; caste regulation ; worker size
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The effect of workers size frequency distribution on colony development was studied in 12 young colonies ofB. terrestris. By replacing the original workers with workers of determined size, colonies constituting small, large or mixed size nursing workers were created. The nursing workers size frequency distribution did not influence the average size of the newly emerged workers, nor their size frequency distribution. In contrast, the number of emerging workers and number of egg cells constructed by the queen in colonies with large workers were higher than in colonies with small workers. The small number of emerging workers is explained by prolonged duration of larval time in response to sub-optimal feeding in colonies of small workers. The higher number of egg cells constructed by the queens is supposed to be in response to the number of new cocoons available, or to better condition of the brood.
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    Insectes sociaux 41 (1994), S. 315-325 
    ISSN: 1420-9098
    Keywords: Eusocial ; phylogeny ; Halictus ; allozymes ; sweat bees
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Halictine bees exhibit an enormous diversity of solitary and social colony structures. To investigate social evolution in the genusHalictus, phylogenies of 15 species of the subgeneraH. (Halictus) andH. (Seladonia) were constructed based on protein electrophoretic data. Solitary, social, and socially polymorphic species were included.Halictus (Seladonia) apparently rendersH. (Halictus) paraphyletic. The common ancestor ofH. (Halictus) andH. (Seladonia) was probably social or socially polymorphic. This implies that some solitary and socially polymorphic species, such asH. confusus andH. tumulorum, represent evolutionary reversals from a completely eusocial condition to the solitary condition that is thought to be primitive for the subfamily as a whole.
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  • 55
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    Insectes sociaux 41 (1994), S. 395-400 
    ISSN: 1420-9098
    Keywords: Eusociality ; habitat ; defense ; ecology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary I hypothesize that three conditions, (1) food-shelter coincidence, (2) strong selection for defense, and (3) ability to defend, are sufficient, although not necessary, for the evolution of eusociality in group-living animals. Reasons for this association between ecology and eusociality include extremely high value of the habitat, possibilities for habitat inheritance, high relatedness in claustral situations, self-sufficiency of juveniles, greater ability of workers to reproduce, and trade-offs between defensive ability and dispersal.
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    Insectes sociaux 41 (1994), S. 379-394 
    ISSN: 1420-9098
    Keywords: Wasps ; Vespula ; competition ; honeydew ; foraging ; Nothofagus forest
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Honeydew is a sugary secretion of beech scale insects (Ultracoelostoma spp.). Two introduced species of wasps forage on the sugar droplets in New Zealand beech forests. We hypothesize that competition between them may explain whyVespula germanica has become locally extinct in beech (Nothofagus) forest invaded byV. vulgaris. Changes in behaviour of the two wasp species in response to changes in the honeydew resource were monitored. Foraging and rainfall separately and together reduced the honeydew standing crop. In response to the standing crop decreasing, more wasps were found on honeydew trees, they became less active, spent more time lapping the tree surface, and ingested drops of honeydew at a slower rate.V. vulgaris was more active, and obtained drops and energy at a higher rate thanV. germanica. These behavioural differences may lead to competitive advantages affecting queen size and possibly survival.
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  • 57
    ISSN: 1420-9098
    Keywords: Polistes wasps ; nest founding ; workers ; behavioral flexibility ; hibernation
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    Notes: Summary First descendants' founding ability was tested inP. dominulus colonies by experimentally removing the original nests and queens 21–24 days after the first emergence. Foundation tests were carried out after three different periods had elapsed after the removal and the results were analyzed with regards to the effects of participation in social tasks, duration of stay within the colony and seasonal factors. 1.Immediately after the removal, the foundations that occurred were performed almost entirely by workers, regardless of the duration of their stay within the colony. The number of foundations depended on the season in which the females had emerged. 2.Two months and four months after the removal, foundations were made by only a small number of females (workers and non-workers). These females, which were therefore able to found a nest the year they were born, were mostly among the very first-born individuals in the colonies. 3.The following year after hibernation: females (workers and non-workers) which had stayed for only a short time within the colony (1–15 days) had the highest survival rates. The foundation rates among the surviving females depended only on seasonal factors, since the foundation rates were higher among the non-workers which had emerged later in the season. The results throw some light on the first descendants' nest-founding potential in colonies developing under natural conditions, where many workers in fact stay for only a short time at the nest.
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  • 58
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    Keywords: Key words: Caste-ratio dynamics, division of labor, foraging frequency, open-air foraging, social behavior.
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    Topics: Biology
    Notes: Summary: The temporal dynamics and social interaction in the foraging activities of the open-air processional termite Hospitalitermes (Termitidae, Nasutitermitinae) were studied in Borneo, Southeast Asia. H. medioflavus and H. sp. A tended to forage from evening to the next morning. On average foraging activity occurred every 3.2 days. Some synchronization of foraging events among colonies was observed, which appeared to be caused by rainfall levels.¶ Temporal dynamics during foraging activity was observed in detail using a photographic method for two species; H. medioflavus and H. rufus. Roughly 300,000 to 500,000 individuals participated in a single foraging event in both species. The soldier ratio was highest at the beginning and the end of the activity. Temporal patterns of behavior were different between soldier, major worker, medium worker and minor worker during foraging. The patterns of behavior are consistent with their tasks in the foraging activity. Soldiers lead the foraging column and protect it, major workers act as food carriers in the earlier stage while medium workers become the dominant food ball carriers in the later stage, and minor workers play the role of gnawers. Therefore, caste composition changes during foraging activity. Similar behavioral tendencies were recognized in both species. Measurement of workers' body weights revealed that workers not only carry balls of food from foraging sites but also feed directly at the foraging sites.
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    Insectes sociaux 45 (1998), S. 33-41 
    ISSN: 1420-9098
    Keywords: Key words: Wasps, nesting sites, palm trees, Astrocaryum sciophilum, French Guiana.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary: In the edge of the rain forests in French Guiana, the large leaves of young Astrocaryum sciophilum, a palm tree with long thin spines (up to 9 cm) along their central vein, shelter significantly more mason as well as social wasps' nests, than leaves of other plants. Other such plants include older conspecific individuals with spines, but compound leaves, and young Bactris simplifrons, a palm tree with similar leaves but devoid of spines. The choice of these leaves is due to the association of two factors: (1) these large leaves with a concave underside offer good protection against inclement weather, and (2) the spines on which the wasps' nests are anchored serve as "acquired pedicels", offering protection against ant predation. As a consequence, the wasps' nests are found under these leaves in both inter- and intraspecific clusters.
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  • 60
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    Keywords: Key words: Isoptera, Rhinotermitidae, Reticulitermes, agonistic behavior.
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    Notes: Summary: Displays of intraspecific and interspecific overt agonistic behavior between colonies of Reticulitermes flavipes (Kollar) and colonies of Reticulitermes virginicus (Banks) were observed in laboratory assays. All possible combinations of arena sizes (1.3, 3.5, 6.0, and 9.0-cm) and group sizes (1, 2, 5 and 10 workers per arena) were assessed for effects on interspecific and intraspecific agonism. Agonistic behavior was scored positive in arenas if half or less of the starting number of termites was alive after 24h. Thirty-six percent of arenas with interspecific pairings were agonistic in all combinations tested while 4.5 % of arenas with intraspecific combinations showed aggression (N = 544 and N = 288, respectively). Two interspecific pairings provided scores that were not statistically different from intraspecific combinations. These assays indicate that evidence of overt agonism between worker termites from these two Rhinotermitid species is not a reliable indicator to differentiate species. Encounters in the two larger arena sizes resulted in significantly more agonism than the two smaller arena sizes. Group size had little apparent effect on the frequency of positive agonistic interactions. Possible reasons for the variable overt agonism scores are discussed.
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    Insectes sociaux 43 (1996), S. 1-15 
    ISSN: 1420-9098
    Keywords: Colony defense ; sterile soldiers ; aphids ; galls ; simulation
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    Topics: Biology
    Notes: Summary Colony defense has been reported in a limited number of species of aphids. This paper examines which life-historical traits have promoted the evolution of colony defense using two kinds of deterministic simulation models. These models postulate that first-instar larvae can counterattack predators and that the duration of this instar stage is a variable, subject to selection. Prolonging the first-instar span increases the proportion of defenders in the colony, while it results in a delay in reproduction. By calculating the optimal first-instar span, the optimal defensive effort of a colony under various ecological conditions could be estimated. Simulations based on the general model, which regards the number of adults maturing in a period as performance, predicted that a lower birthrate leads to a longer first-instar span (larger investment in defense). This condition also allowed the evolution of dimorphism in the first-instar span, which may ultimately result in the appearance of soldiers. Where birthrate declines with time, the first-instar span was predicted to be prolonged in later stages. Colony duration had little influence on the optimal first-instar span if the season is long enough to repeat generations. The galling-aphid model that assumes a fixed number of generations predicted that a longer duration of colonies leads to a longer first-instar span, but that birthrate has little influence on the optimal first-instar span. A tendency in defense reported in pemphigid aphids was consistent with the prediction from the galling-aphid model.
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  • 62
    ISSN: 1420-9098
    Keywords: Key words: Gallery forest, Ivory Coast, savanna, termites, thermoregulation.
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    Topics: Biology
    Notes: Summary: We determined density and distribution of the mounds of the fungus-cultivating termite Macrotermes bellicosus (Smeathman) in two habitats (shrub savanna and gallery forest) of the Comoé National Park (Ivory Coast, West Africa). We measured height, basal width, and interior and exterior temperatures of mounds in both habitats, and established a new method to measure the surface area of mounds.¶ In the shrub savanna, M. bellicosus mounds reached high densities (up to 22.7 live mounds/ha), whereas in the gallery forest mounds could only be found in open stands and at comparatively low densities (up to 6.5 live mounds/ha).¶ Ambient temperature had an important influence on the architecture of the mounds. Mounds in the warmer, but thermally more fluctuating shrub savanna were more structured with many ridges and turrets than the dome-like, compact mounds in the cooler, more equable gallery forest. The surface complexity was quantified as the ratio of surface (= rsf), which is the quotient of the real surface to the minimal possible surface of an ideal cone of the same height and basal width as the measured mound. By manipulating ambient temperatures, we were able to demonstrate causal relationships between temperature and mound shape. In the gallery forest, where shade was reduced surface complexity increased on mounds.¶Despite their different architecture in the gallery forest, the M. bellicosus colonies could not completely compensate for the cooler environment and had a lower than optimal nest temperature. We speculate that this might be caused by the need for a sufficient surface for gas exchange. The gallery forest is a suboptimal habitat for M. bellicosus, because of lower than optimal nest temperatures. This might limit M. bellicosus to open stands in the gallery forest and may explain its surprisingly low abundance in this habitat.
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    Insectes sociaux 45 (1998), S. 67-77 
    ISSN: 1420-9098
    Keywords: Key words: Size polymorphism, microgynes, reproductive strategies, dispersal.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary: With recent findings of an unexpected variability in the reproductive behaviour of ant sexuals, their morphology has become an area of major evolutionary interest (Heinze and Tsuji, 1995). Here we report on the occurrence of two queen morphs in Leptothorax rugatulus (Hym., Formicidae): Microgynes (small queens), exceeding worker-size only marginally, and macrogynes, which are, typically for the subgenus Myrafant, about twice as big as their workers. The frequency distribution of queen-size is clearly bimodal, in contrast to worker- and male-size. The average size of queens is highly correlated with the size of daughters in field-collected colonies, whereas within colonies no correlation between the average queen-size and the size of workers or males exists. This gives additional support that size-dimorphism is due to a specific, transmissible size reduction of the microgynes which could be based on genetics, the environment or both. This reduction is quasi-isometric, with a slightly smaller thorax-to-head ratio in microgynes, and scanning electron microscopy does not reveal any significant degeneration of the pterothorax, ocelli or number of ommatidia. The frequency of microgynes at different sample sites is highly variable, correlating well with the prevailing social structure in the respective subpopulations. Indeed, the majority of macrogynes is found in monogynous colonies, while microgynes abound in polygynous ones, which is strong evidence for an alternative dispersal tactic. However, the expected correlation to altitude or latitude was not found and further investigations are needed to reveal proximate and ultimate causes of this prevalent polymorphism between two types of female ant reproductives.
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    Insectes sociaux 45 (1998), S. 85-96 
    ISSN: 1420-9098
    Keywords: Key words: Chemical communication, Dufour's gland, recruitment, trail following, Messor capitatus.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary: Some aspects of the chemical communication system employed by the harvesting ant Messor capitatus during foraging were investigated in the laboratory. After locating a conspicuous food item the scouts return home dragging their gaster on the ground. Once inside the nest they run among nestmates and perform an excited motor display. Soon after, groups of workers rush out and move towards the food. Bioassays of different gland extracts showed that nestmates are activated and induced to leave the nest by substances from Dufour's gland. This gland was also found to be the source of the orientation-recruitment trails by which foragers reach newly discovered food sources. The bioassays showed that poison gland extracts are also active in inducing trail following. However, this response was accompanied by typical aggressive reactions by tested ants, suggesting that the poison gland is involved in alarm communication and recruitment towards a source of danger rather than in foraging activities. Some features of the Dufour's gland trail (such as its durability and lack of colony-specificity) are discussed with regard to the ecological requirements of this species.
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    Insectes sociaux 45 (1998), S. 113-124 
    ISSN: 1420-9098
    Keywords: Key words: Leptothorax, Formicoxenini, ergatoid queens, intermorphic queens, intercastes, morphology.
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    Topics: Biology
    Notes: Summary: The terminology for ant females which are morphologically intermediate between “normal”, originally winged queens and workers teems with ill-defined terms, such as “ergatogyne”, “apterogyne”, or “gynaecoid worker”. The terminology proposed by Peeters (1991a) gets rid of most of these terms but fails to distinguish between sporadically occurring “intercastes”, reared due to “mistakes” in caste differentiation, and “intermorphic queens”, which are the ordinary female reproductives in many colonies of formicoxenine ants. A detailed examination of development, morphology, and occurrence of the latter suggests that intermorphic queens are more similar to ergatoid queens (sensu Peeters, 1991a) than to “intercastes”, and should not be comprised under the latter term.
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    Insectes sociaux 45 (1998), S. 97-109 
    ISSN: 1420-9098
    Keywords: Key words: Halictidae, pleometrosis, social evolution.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary: Female sweat bees in the species Halictus ligatus exhibit a wide range of reproductive roles, ranging from typically foundress or queen-like to typically worker-like. Nests are founded in spring and most are haplometrotic, that is, founded by a single foundress. A few (up to 12 %) are pleometrotic, founded by 2-6 foundresses. Variation in the proportion of multifoundress nests from year to year and from place to place suggests an adaptive basis for pleometrosis. We studied the demographic and social characteristics of 23 pleometrotic nests in an aggregation of 250-300 nests near Victoria, Ontario, in 1984, 1990, and 1991. In pleometrotic associations, dominant foundresses behaved in a manner typical of mid-summer, haplometrotic queens, while subordinates behaved like mid-summer workers. Dominant foundresses tended to be larger than subordinates. Pleometrotic nests were significantly more likely than haplometrotic nests to produce brood, and they also produced more workers. However, this early advantage did not result in the production of more reproductive brood per nest, nor did pleometrotic foundresses experience higher productivity per foundress than did haplometrotic foundresses. Relatively low relatedness among various categories of brood implied that subordinate foundresses were not closely related to dominants. We suggest that pleometrosis most likely results from accidental encounters between spring foundresses as they leave their hibernacula. Once formed, such associations confer a survival advantage on the nest as a whole, but do not result in greater reproductive brood productivity.
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    Insectes sociaux 45 (1998), S. 125-134 
    ISSN: 1420-9098
    Keywords: Key words: Life history, kleptoparasitism, interspecific relationships, sociality, spiders.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary: Among spiders, some species could be qualified as colonial. Individuals may live alone or in colonies where each spider exploits its own capture web in a communal network. We compared solitary with colonial life in Cyrtophora female populations from South-East Sicily in 1992 and 1993. We used 6 parameters to describe and compare the populations: spider size, web size, egg production, prey captured, presence of kleptoparasites and their size.¶ Spiders living in colonies did not differ in size from solitary spiders.¶ The webs of colonial spiders were smaller than those of solitary spiders.¶ The number of prey captured and their size did not differ between the two types of spiders.¶ Solitary spiders produced more eggs than colonial individuals.¶ Kleptoparasite spiders Argyrodes gibbosus were more numerous in the webs of solitary spiders than in the webs of colonial spiders and there were more solitary webs infested by kleptoparasites in 1992. The kleptoparasites were larger in colonial webs than in solitary ones. Another species of spider, Holocnemus pulchei, spun its own web in the network of the web of Cyrtophora. The number of Holocnemus per web did not differ between solitary and colonial Cyrtophora.¶ Results are discussed by referring to what it is known in other temporarily social spiders.
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    Insectes sociaux 45 (1998), S. 191-195 
    ISSN: 1420-9098
    Keywords: Key words: Group effect, latency time, fungus-growing termites, building behavior, bees, aggressiveness.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary: We suggest that group effect need not be invoked to explain the differences in latency times exhibited by groups of different sizes in the initiation of building in the termite Macrotermes subhyalinus (Rambur). A simple, alternative, model is presented, that is fully consistent with experimental data.
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    Insectes sociaux 45 (1998), S. 301-313 
    ISSN: 1420-9098
    Keywords: Key words:Cataglyphis, worker odour, queen odour, Formicidae, polydomy.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary: We investigated the queen's effect on the cuticular hydrocarbon profile of workers in the monogynous and polydomous species Cataglyphis iberica. Within each of the three colonies tested, workers were separated for three months in queenright and queenless groups. After regrouping, nestmate recognition remained unchanged but the duration of antennal interactions between workers previously separated increased relative to controls. Separated groups presented slightly divergent cuticular hydrocarbon profiles which may induce the longer antennations. A quantitative analysis of major cuticular hydrocarbons showed that the total amount per unit of cuticular surface area remains similar between the two castes; but queens had higher quantities of n-alkanes than workers. The lack of a queen did not affect the workers' cuticular hydrocarbon profile in queenless groups. Indeed, the profile of queenless workers remained significantly different from the queen profile as did that of queenright workers. These results show that queens are not at the origin of the hydrocarbons' colonial profile. Two recognition processes seem to coexist within C.iberica colonies: nestmate discrimination based on the colonial odour which includes all nestmate workers, and a queen caste-specific odour. In a polydomous species such as C.iberica, the queen does not seem to contribute more than any other nestmate to the colonial odour, which probably derives from worker cues, confirming the existence of a "Gestalt" colonial odour.
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    Insectes sociaux 45 (1998), S. 315-333 
    ISSN: 1420-9098
    Keywords: Key words: Soldier, caste, evolution, ants.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary: The traditional hypothesis that ant soldiers originate from large size workers is rejected in favour of their direct origin from gynes. This conclusion is supported by the first report of soldiers smaller than workers, by an intercaste morphometric comparative analysis by means of D'Arcy Thompson's transformation grids and by phylogenetic studies on Cephalotes showing that the cephalic shield appeared ancestrally among soldiers and only later among gynes. The same conclusion flows from facts already known but hitherto misunderstood and stressed in this paper such as: 1) there are species of Cephalotes with soldiers with incomplete cephalic shield and no gyne shield and other species with complete soldier shield but only incomplete gyne shield; 2) the phragmotic behaviour is exercised by workers and soldiers and not by gynes but its morphological correlate, i.e., the shield-shaped head, occurs among soldiers and gynes and not in workers. These observations prove that the selection pressure for the shield morphology acts on workers and soldiers and not on gynes but its morphological correlate actually appears first in soldiers, later in gynes and never in workers. These data sharply contrast with a worker origin of soldiers and are perfectly consistent with the hypothesis of a separate origin of soldiers directly from gynes.
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    Insectes sociaux 45 (1998), S. 349-368 
    ISSN: 1420-9098
    Keywords: Key words: Social evolution, sex allocation, kin selection, comparative studies, Exoneura, Apidae.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary: Comparative studies provide one of the most powerful means of assessing the relative roles of selective agents underlying social evolution in insects. Because of the wide variation in social organisation, sex allocation and ecological traits within and between species of allodapine bees, this group provides a wealth of material for such comparative work. Recent studies on Australian allodapine bees are reviewed here and their consequences for understanding social evolution are discussed. Studies to date suggest the following trends: (i) benefits of group living appear to be linked to preventing brood failure rather than to increased brood rearing efficiency; (ii) female-biased sex allocation, when it occurs, is linked to benefits of group living and kinship among nestmates, and is probably mediated via local fitness enhancement; (iii) female-biased sex allocation patterns do not usually coincide with opportunities for sib-rearing and are therefore unlikely to facilitate eusociality; (iv) relatedness within colonies is usually high, but in some species females will nest with unrelated females if kin are not available; and (v) phylogenetic studies suggest that opportunities for sib-rearing, arising from brood development patterns and colony phenology, are plesiomorphic for the exoneurine group, but in at least one phylogenetically distal clade, Exoneura sensu stricto, the evolution of large group size and social complexity coincides with the loss or reduction of opportunities for sib-rearing. Assured fitness return models may be applicable to weakly social allodapine species, but do not predict patterns of eusociality. Instead, Australian studies suggest that the evolution of large group size and marked reproductive skew is linked with the need to defend against enemies at the nest, rather than high levels of relatedness, female biased sex allocation or opportunities to rear siblings.
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    Insectes sociaux 46 (1999), S. 315-322 
    ISSN: 1420-9098
    Keywords: Key words:Bombus terrestris, bumble bee, larval feeding, caste differentiation.
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    Topics: Biology
    Notes: Summary: The duration of feedings received by Bombus terrestris larvae was studied using video-recordings. In the last days of development all larvae received feedings mainly of long duration. Worker larvae of the third brood received significantly longer feedings than worker larvae reared in the other broods. Throughout the development queen larvae and worker larvae received feedings of similar duration. Male larvae received shorter feedings than both kinds of female larvae. Therefore, the duration of feedings seems to be associated to the sex and stage of development of the larvae.¶The causes of the long-duration feedings seem not to be related to the amount of food provided, workers' age and size, to the workers' abdominal contraction or to the amount of pollen in the larval food. Perhaps the feeding duration is caused by the viscosity of the food, which is a consequence of the presence of pollen grains, sugar and glandular material. Although the precise amount of pollen was not measured, the differences in colour showed clearly that the larval food samples contained variable quantities of pollen grains. Some of the samples did not contain any pollen at all.¶It is suggested that the duration of feedings may be related (among other factors) to the presence of glandular material (proteins and enzymes) which is added to the larval food. This could be especially important for queen larvae in the last phase of their development. Because they have a long development and are fed with a high frequency they might receive large amounts of these substances. This could help them to grow more efficiently using a relatively smaller amount of pollen than expected.
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  • 73
    ISSN: 1420-9098
    Keywords: Key words: Pre-mating behaviour, gyne, abdomen enlargement, Melipona beecheii, stingless bee.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary: The behaviour of gynes of Melipona beecheii in queen-deprived colonies was studied. The period after emergence until acceptance is characterized by agonistic behaviour of workers towards the gynes. The gynes escaped from this worker aggression by hiding in the periphery of the nest, by performing rapid turn-arounds once grabbed by a worker, and "feigning death". Between acceptance and nuptial flight, gynes spent most of their time in pushing, hiding, and antennal contact with workers, and self-grooming or food solicitation. After the nuptial flight the queen's behavioural repertoire shifted to less pushing and food solicitation, to an increase in standing, tapping and antennal contact.¶Accepted gynes had a significantly more prolonged abdomen inflation than gynes that were eliminated.¶An hypothesis is presented to explain how abdomen enlargement and behavioural development influences the acceptance of gynes and the establishment of a dominance relation with workers under queenless conditions.
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    Pure and applied geophysics 132 (1990), S. 21-47 
    ISSN: 1420-9136
    Keywords: Wave scattering ; free surface ; heterogeneity ; body ; Rayleigh ; and Love waves
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The seismic coda is usually thought to be composed of waves scattered from the heterogeneities in the earth. Three classes of scattering mechanisms have been recognized: repeated specular reflection of primary waves in a uniformly layered structure, volume scattering of primary waves from localized volume heterogeneities, and scattering of primary waves from irregularities in an otherwise generally layered structure. The presence of the earth's surface complicates the description of all these scattering phenomena whenever the scattering obstacles are near or at the surface. In this paper I review work which demonstrates the effects of scattering near the earth's surface, emphasizing three general areas of investigation: scattering of body waves from an irregular free surface, scattering of body waves in irregular layers, and propagation of surface waves across irregular topography or in irregular wave guides. Most of the effects of importance have been recognized in model studies of idealized geometries. Observational evidence in support of the model studies exists, but is often inferred. Few controlled experiments to measure scattering have been performed. Topography can focus or defocus incident body waves and can convert body waves to surface waves and vice versa. Irregular surface layers can amplify incident body waves, couple body and surface waves, and produce resonances in spatially limited low velocity valley structures and highly irregular layers. Love wave propagation is highly sensitive to irregularities in a wave guide. Love wave dispersion measured over irregularly layered media can be quite different from the dispersion of the mean plane layered structure beneath the receiver array. Rayleigh wave dispersion is far less sensitive to smooth irregularities in a wave guide and is usually representative of the mean structure beneath the receiving array.
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    Pure and applied geophysics 132 (1990), S. 245-267 
    ISSN: 1420-9136
    Keywords: P wave amplitudes ; focussing ; three-dimensional wave propagation
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    Notes: Abstract Short-period teleseismicP waves from the Nevada Test Site (NTS) show systematic variations in amplitudes and travel times, with low amplitudes corresponding to fast travel times, suggesting elastic focussing-defocussing effects. Also, the azimuthal amplitude and travel time patterns for events at the Pahute Mesa subsite are systematically different from those at the Yucca Flat subsite, indicating the presence of a near-source component in both the amplitude and travel-time variations. This component is isolated by removing the mean station pattern for all of NTS from the observations. A very-near-source component in the Pahute Mesa observations is also isolated by removing subsite station means from the measurements, whereas the Yucca Flat observations exhibited no coherent very-near-source component. These anomalies are back-projected through laterally homogeneous structure to form thin lens models at various depths. Travel-time delays are predicted from the amplitude variations using the equation for wavefront curvature. The long-wavelength components of the predicted and observed time delays correlate well, at depths of 25 km for the very-near-source component under Pahute Mesa and 160 km for the regional component under NTS. The time delay surfaces predicted by the amplitudes at these depths are mapped into warped velocity discontinuities suitable for the calculation of synthetic seismograms using the Kirchhoff-Helmholtz integral formulation. Both the intersite (near-source) and intrasite (very-near-source) differences in amplitudes are qualitatively predicted very well, although the range of variation is somewhat underpredicted. This deficiency is likely due to the destructive interference of anomalies inherent in back-projection to a single layer.
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  • 76
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    Pure and applied geophysics 132 (1990), S. 363-400 
    ISSN: 1420-9136
    Keywords: Crustal scattering ; apparent attenuation ; anisotropy ; physical models
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    Notes: Abstract We study wave propagation through isotropic and anisotropic scatterer distributions in order to observe azimuthal variations in velocity and apparent attenuation. Using thin aluminum plates as physical models, we obtained seismograms for compressional and shear wave propagation through heterogeneous media. Three random distributions of scatterers are studied: circular scatterers in isotropic distributions (modeling circular scatterers), elongated scatterers in isotropic distributions (modeling randomly oriented elliptical scatterers), and elongated scatterers in anisotropic distributions (modeling aligned elliptical scatterers). All scatterers had approximately the same cross-sectional area and were filled with epoxy in order to reduce the impedance contrast. In addition to seismograms recorded for no scatterers, seismograms were recorded for several scatterer volume fractions. Azimuths were measured relative to the long axis of the aligned elongated scatterers. Velocities were calculated using travel times and phase shifts at low frequencies. The velocities measured from the data were compared to simple low-frequency average-velocity theories based on thin lamellae or on distributions of penny-shaped cracks. The apparent attenuation for different scatterer distributions was computed using spectral ratios. Comparisons of the results for circular and randomly oriented elongated scatterers were made to determine the effects of scatterer shape. As expected, the circular and randomly oriented elongated scatterers showed no systematic azimuthal variation in velocity. The velocity anomalies were systematically larger for the randomly oriented elongated scatterers than for the circular scatterers. Both methods of theoretical estimation for the isotropic velocities produced velocities significantly larger than those measured. The spectral ratios showed more apparent attenuation for the randomly oriented elongated scatterers than for the circular scatterers. Comparisons of the results for the randomly oriented and aligned elongated scatterers were made to determine the effects of anisotropy in the scatterer distribution. Compressional waves for the aligned elongated scatterers with wave propagation parallel to the scatterers had larger velocities than for the aligned elongated scatterers with wave propagation perpendicular to the scatterers for all velocity calculations. Shear wave velocities were complicated by an anomalous phase change in the shear wave seismograms for azimuths less than 40° and were not as conclusive. The general trend of the theoretical velocities is similar to the velocities calculated from the data. There are, however, what appear to be significant differences. The spectral ratios showed more apparent attenuation for the randomly oriented elongated scatterers than for the aligned elongated scatterers with wave propagation parallel to the scatterers, and less attenuation than for the aligned elongated scatterers with wave propagation perpendicular to the scatterers.
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  • 77
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    Pure and applied geophysics 132 (1990), S. 457-479 
    ISSN: 1420-9136
    Keywords: Turbulence ; mesures aéroportées ; fluctuation de pression ; presso-corrélations
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    Topics: Geosciences , Physics
    Notes: Résumé Nous avons décrit dansBardeau et al. (1987), la réalisation, le fonctionnement et les tests d'un microdébitmètre basé sur l'anémométrie à fil chaud. Il a été particulièrement montré que cet appareil était bien adapté aux mesures de pression et pression différentielle avec une grande sensibilité et une très faible constante de temps. Nous présentons ici les applications qui ont été faites de ce capteur aux mesures à haute résolution à bord d'avions instrumentés pour la recherche atmosphérique. L'avion utilisé était spécialement équipé pour les mesures de turbulence et permettait donc l'acquisition d'un grand nombre de paramètres indispensables à l'analyse des données de ce capteur. Dans les applications aéronautiques qui ont été faites, le capteur a surtout été utilisé en tant que variomètre. Les comparaisons avec les mesures standards d'altitude par pression et couplages pression-données inertielles montrent que cet instrument pourrait apporter une contribution intéressante dans le domaine de la mesure à haute fréquence des fluctuations de pression.
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  • 78
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    Keywords: magnetic interpretation ; horizontal cylinders ; correlation factors ; least-squares residuals
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    Notes: Abstract Procedures are formulated using the correlation factors between successive least-squares residual magnetic anomaly profiles due to long horizontal cylinders for interpreting the three principal anomalies (vertical, horizontal, and total). It is demonstrated that correlation values can be used to determine the depth to the center of the buried structure and the index parameter. Procedures are also formulated to estimate the amplitude coefficient. Two worked examples using theoretical data show the effectiveness of the present method.
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  • 79
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    Keywords: Hilbert transform ; S.P. anomalies ; convolution ; abscissae ; amplitude ; error analysis ; Cuddapah basin
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    Notes: Abstract Self-potential anomalies due to two-dimensional inclined sheet of finite depth extent are analysed from their horizontal and vertical derivatives via the Hilbert transform. The depths to the top and bottom of the sheet and the inclination are obtained by means of simple mathematical expressions. The method is applied to a theoretical example and to a field S.P. anomaly over a sulphide deposit in the Kalava fault zone of Cuddapah basin, India. The presence of random noise is analysed for various levels and its effect is discussed. This interpretation process can be automated for all practical purposes by simple programming.
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    Pure and applied geophysics 132 (1990), S. 151-173 
    ISSN: 1420-9136
    Keywords: Scattering ; wave propagation ; seismic waves ; core-mantle topography ; inhomogeneities
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    Notes: Abstract Statistical properties of small-scale inhomogeneities (wavelengths between 20 and 70 km) near the core-mantle boundary are inferred from scattered core waves. Observations of scattered core waves at large seismic arrays and worldwide networks indicate that the inhomogeneities have a global nature with similar characteristics. However, there may exist a few regions having markedly stronger or weaker strengths. Scattering by volumetric inhomogeneities of about 1% inP-wave velocity in the lower mantle or by about 300 m of topographic relief of the core-mantle boundary can explain the observations. At present it is not possible to rule out either of these two alternatives, or a combination of both.
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  • 81
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    Pure and applied geophysics 132 (1990), S. 175-196 
    ISSN: 1420-9136
    Keywords: Wave propagation ; seismic waves ; heterogeneities ; lithosphere
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    Notes: Abstract Adopting the spectral approach, we derive the formulation of angular coherence and transverse coherence of transmission fluctuations. Our derivation and results provide new insight on transmission fluctuation analysis. A review of research work on fluctuation analysis using observations at large seismic arrays such as LASA and NORSAR-follows. We point out that the model of a single-layer Gaussian medium cannot explain the angular coherence of NORSAR data and a more general model of a non-Gaussian, multi-scale, vertically inhomogeneous random media is needed. The model of a two-layer power-law medium proposed by Flatté and Wu is among the simplest of such models.
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  • 82
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    Pure and applied geophysics 132 (1990), S. 495-504 
    ISSN: 1420-9136
    Keywords: Radon ; S.S.N.T.D. ; geochemical tracer ; fault ; atmospheric parameters ; enhancement technique
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    Notes: Abstract The existence of a suspected geological fault has been confirmed using Solid State Nuclear Track Detectors (SSNTDs) by measuring radon concentration variations in the upper soil above its inferred position. The results obtained prompted us to increase the natural radon signal in the soil, using an additional radon source; this “enhancement technique,” has been experimentally checked with SSNTD detectors.
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  • 83
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    Pure and applied geophysics 132 (1990), S. 583-597 
    ISSN: 1420-9136
    Keywords: Reflection ; seismology ; conservation ; inversion
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    Notes: Abstract We show that the time-dependent wave equation in both one and two spatial dimensions possesses quantities which are globally conserved. We show how these conserved quantities can be used to determine the characteristic impedance, the rock density and the elastic constant of the rock. We also demonstrate that the conserved quantities possess the capability of determining and/or bracketing the unknown component of the direct pressure response, which is required to begin downward continuation algorithms. Further, we demonstrate that the conserved quantities are always available irrespective of the source structure in time. Numerical instability, arising if the “filtering” due to the source structure is too harsh, can then be controlled to a degree by demanding that the conserved quantities be indeed conserved.
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  • 84
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    Pure and applied geophysics 132 (1990), S. 533-543 
    ISSN: 1420-9136
    Keywords: Computer ; earthquake ; Hungary ; intensity ; macroseismic ; MSK scale ; questionnaire
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    Topics: Geosciences , Physics
    Notes: Abstract In this paper a computerized method for the intensity estimation from macroseismic observations is presented. The successive steps of the MSK intensity scale (2° to 10°) receives weights according to the observations marked on the earthquake questionnaires. These weights are summed for the individual scale steps. The distribution of these summed weights and their relation to an experimentally chosen function of the criterion make it possible to estimate the appropriate intensity value and its reliability. By computer evaluation of earthquake reports an objective comparison of estimated intensities given by different seismologists can be made, provided that uniform earthquake questionnaires are used. The application of this method will result in more homogeneous intensity data.
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  • 86
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    Pure and applied geophysics 132 (1990), S. 545-568 
    ISSN: 1420-9136
    Keywords: Cracks ; scattering ; attenuation ; phase velocity ; SH waves
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    Notes: Abstract The effect of randomly distributed cracks on the attenuation and dispersion ofSH waves is theoretically studied. If earthquake ruptures are caused by sudden coalescence of preexisting cracks, it will be crucial for earthquake prediction to monitor the temporal variation of the crack distribution. Our aim is to investigate how the property of crack distribution is reflected in the attenuation and dispersion of elastic waves. We introduce the stochastic property, in the mathematical analysis, for the distributions of crack location, crack size and crack orientation. The crack size distribution is assumed to be described by a power law probability density (p(a) ∞ a −γ fora min≤a≤a max according to recent seismological and experimental knowledge, wherea is a half crack length and the range 1≤γ≤3 is assumed. The distribution of crack location is assumed to be homogeneous for the sake of mathematical simplicity, and a low crack density is assumed. The stochastic property of each crack is assumed to be independent of that of the other cracks. We assume two models, that is, the aligned crack model and the randomly oriented crack model, for the distribution of crack orientation. All cracks are assumed to be aligned in the former model. The orientation of each crack is assumed to be random in the latter model, and the homogeneous distribution is assumed for the crack orientation. The idea of the mean wave formalism is employed in the analysis, and Foldy's approximation is assumed. We observe the following features common to both the aligned crack model and the randomly oriented crack model. The attenuation coefficientQ −1 decays in proportion tok −1 in the high frequency range and its growth is proportional tok 2 in the low frequency range, wherek is the intrinsic wave number. This asymptotic behavior is parameter-independent, too. The attenuation coefficientQ −1 has a broader peak as γ increases and/ora min/a max decreases. The nondimensional peak wave numberk p a max at whichQ −1 takes the peak value is almost independent ofa min/a max for γ=1 and 2 while it considerably depends ona min/a max for γ=3. The phase velocity is almost independent ofk in the rangeka max〈1 and increases monotonically ask increases in the rangeka max〉1. While the magnitude ofQ −1 and the phase velocity considerably depend on the orientation of the crack in the aligned crack model, the above feature does not depend on the crack orientation. The accumulation of seismological measurements suggests thatQ −1 ofS waves has a peak at around 0.5 Hz. If this observation is combined with our theoretical results onk p a max, the probable range ofa max of the crack distribution in the earth can be estimated for γ=1 or 2. If we assume 4 km/sec as theS wave velocity of the matrix medium,a max is estimated to range from 2 to 5 km. We cannot estimatea max in a narrow range for γ=3.
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    Pure and applied geophysics 132 (1990), S. 719-731 
    ISSN: 1420-9136
    Keywords: Magnetic interpretation ; pair of sheets ; equivalence to dykes
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    Topics: Geosciences , Physics
    Notes: Abstract Magnetic anomaly profiles over two thin sheets separated by a small distance resemble those of dykes andvice versa. Interpretation of anomalies over a pair of sheets based on the magnetic properties of dykes predicts a dyke whose centre lies midway between the positions of the sheets. The dyke, on the other hand, is magnetically equivalent to a pair of sheets, both lying at the same depth and having the same magnetization. The magnetic anomalies due to a pair of sheets can be interpreted by framing linear equations between the anomalies and their distances measured from an arbitrary reference. Application of this method to anomalies of dipping sheets with a finite depth extent is indicated.
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    Pure and applied geophysics 132 (1990), S. 811-824 
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  • 89
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    Pure and applied geophysics 133 (1990), S. 23-52 
    ISSN: 1420-9136
    Keywords: CodaQ −1 ; scattering ; mainshock area
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    Topics: Geosciences , Physics
    Notes: Abstract A temporal and spatial change of codaQ −1 associated with the occurrence of the North Palm Springs earthquake of July 8, 1986 was studied by using 242 small local earthquakes in the vicinity of the mainshock. We found that the codaQ −1 of earthquakes which occurred before the mainshock was significantly higher than that of the aftershocks in the mainshock area while the codaQ −1 for the surrounding area remained almost constant throughout 1986. CodaQ −1 was determined separately for the lapse time windows of 10 to 20 sec. and 15 to 40 sec. for the period from 1981 to 1987. The result for the time window 10 to 20 sec. showed a peak in codaQ −1 before the time of mainshock at all frequencies. The peak appeared earlier at lower frequencies. There was no significant change in codaQ −1 for the time window 15 to 40 sec., probably because the change was restricted to a small area.
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  • 90
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    Pure and applied geophysics 133 (1990), S. 103-115 
    ISSN: 1420-9136
    Keywords: Reflection travel time ; interval velocities ; layer thickness
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    Notes: Abstract In reflection surveys and velocity analysis, calculations of interval velocities and layer-thicknesses of a multilayered horizontal structure are often based on Dix's equation which requires the travel times at zero offsets and a prior estimate of the root mean squared velocities. In this paper a method is presented which requires only the reflection travel-time data. A set of equations are derived which relate the interval velocity and thickness of a layer to the reflection travel time from the top and the bottom of that layer, the offset distances and the ray parameter. It is shown that the difference of the offset distances and the difference of the picked travel times of any reflected rays with the same value of ray parameter from the top and the bottom of a horizontal layer can be used to calculate the interval velocity and thickness of that layer.
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  • 91
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    Pure and applied geophysics 133 (1990), S. 213-227 
    ISSN: 1420-9136
    Keywords: Indoor radon ; soil radon ; aeroradioactivity ; uranium
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    Topics: Geosciences , Physics
    Notes: Abstract Attempts to predict which geographic areas should be associated with a high percentage of homes with unusually high indoor radon levels in Virginia and Maryland have been based on estimates of soil radon and soil permeability for geological units. This method is found to be less successful and probably less cost-effective than the use of total-gamma aeroradioactivity maps.
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  • 92
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    Pure and applied geophysics 136 (1991), S. 87-101 
    ISSN: 1420-9136
    Keywords: Curie point ; aeromagnetic ; heat flow
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    Topics: Geosciences , Physics
    Notes: Abstract The objective of this study is to understand the nature and extent of the regional geothermal system at depth beneath the area of Greece by constructing the Curie isotherms. Spectral analysis of aeromagnetic data in conjunction with heat flow information revealed an almost inverse linear relation between heat flow and Curie depths and was used to construct the Curie isotherms from the existing heat flow data. The results showed that Curie depths in the area range from about 20 km in western Greece, up to 1 km beneath the Hellenic volcanic arc. These results are consistent with the existing geothermal and geotectonic regime in the area.
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  • 93
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    Pure and applied geophysics 136 (1991), S. 143-154 
    ISSN: 1420-9136
    Keywords: Earthquake statistics ; earthquake hazard ; Vrancea seismogenic region
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    Notes: Abstract A maximum likelihood method is used to estimate the earthquake hazard parameters maximum magnitudeM max, annual activity rate λ, and theb value of the Gutenberg-Richter equation in the Vrancea (Romania) region. The applied procedure permits the use of mixed catalogs with incomplete historical as well as complete instrumental parts, the consideration of variable detection thresholds, and the incorporation of earthquake magnitude uncertainty. Our imput data, comprises 105 historical earthquakes which occurred between 984 and 1934, and a complete data file containing 1067 earthquakes which occurred during the period 1935–30 August, 1986. The complete part was divided into four subcatalogs according to different thresholds of completeness. Only subcrustal events were considered, and dependent events were removed. The obtained $$\hat b$$ value (=0.65) is at the lower range of the previously reported results, but it appears concurrent with conceptual and observational facts. The same concerns inferred value of $$\hat M$$ max = 7.8 and activity rate $$\hat \lambda $$ 4.0 = 5.34.
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  • 94
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    Pure and applied geophysics 133 (1990), S. 429-446 
    ISSN: 1420-9136
    Keywords: Attenuation ; maximum entropy ; surface waves
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    Notes: Abstract A new technique for calculating interstation Green's functions and attenuation coefficients for seismic surface waves is presented. The interstation Green's function is evaluated from the autocorrelation functions of the seismograms, which are obtained from a maximum entropy process. Since a data-invariant time window is not used, the evaluated Green's functions gives reliable information on both the amplitude and the phase spectra of the system. This new technique is compared with other methods by applying them to both synthetic and real data from a path in the Canadian shield.
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  • 95
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    Keywords: Surface waves ; transversely isotropic ; liquid saturated porous solid ; dispersion ; Rayleigh type waves ; nondissipative porous media ; frequency equation ; phase velocity
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    Notes: Abstract Dispersion of Rayleigh-type surface wave is studied in a homogeneous transversely isotropic elastic layer overlying a nondissipative liquid-saturated porous solid half-space and lying under a uniform layer of homogeneous liquid. The frequency equation in the form of ninth-order determinant is obtained. Special cases have been deduced by reducing the depth of the layers to zero and by changing the transverse isotropic layer to an isotropic layer. Dispersion curves for the phase velocity have been plotted for a particular model.
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    Pure and applied geophysics 133 (1990), S. 691-712 
    ISSN: 1420-9136
    Keywords: Rossby waves ; ray theory ; oceanic mixed layer
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    Notes: Abstract Rossby wave propagation in the presence of a nonseparable Brunt-Väisälä frequency,N(y,z), and the associated geostrophic zonal flow,U(y,z), is examined in this paper. The usual quasi-geostrophic potential vorticity equation only includes vertical variations in Brunt-Väisälä frequency (i.e.N(z)). We derive a linearised quasi-geostrophic potential vorticity equation which explicitly includesN(y, z), where variations inN may occur on the internal Rossby radius length scale. A mixed layer distribution that monotonically deepens in the poleward direction leads to a nonseparableN(y,z). The resulting meridional pressure gradient is balanced by an eastward zonal geostrophic flow. By assuming mixed layer depth changes occur slowly, relative to a typical horizontal wavelength of a Rossby wave, a local analysis is presented. The Rossby wave is found to have a strongly modulated meridional wavenumber,l, with amplitude proportional to |l|−1/2. To elucidate whether the modulations of the Rossby wave are caused by the horizontal variations inN orU we also consider the cases where eitherN orU vary horizontally. Mixed layer depth changes lead to largestl where the mixed layer is deepest, whereasl is reduced in magnitude whereU is nonzero. When bothU(y,z) andN(y,z) are present, the two effects compete with one another, the outcome determined by the size of |c|/U max, wherec is the Rossby wave phase speed. Finally, the slowly varying assumption required for the analytical approach is removed by employing a numerical model. The numerical model is suitable for studying Rossby wave propagation in a rectangular zonal channel with generalN(y, z) andU(y, z).
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    Pure and applied geophysics 133 (1990), S. 733-748 
    ISSN: 1420-9136
    Keywords: Nonlinear coherent structures ; modons ; IG eddies ; local multiple equilibria ; long Rossby waves ; potential vorticity
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    Notes: Abstract It is demonstrated that nonlinear Rossby modes, such as modons and IG eddies, can be excited in planetary fluids by a sufficiently strong forcing of potential vorticity. When a weak forcing is balanced with a weak dissipation, two (linear and nonlinear) equilibrium states can be produced, depending on the initial condition. When the fluid is inviscid, a sufficiently strong steady forcing may generate a sequence of propagating nonlinear eddies. A weak forcing, by contrast, only generates linear Rossby waves. The criterion which divides the high amplitude nonlinear state and the low amplitude linear state may be interpreted in terms of a ratio of a time necessary to force the eddy to a time for a fluid particle to circulate about the nonlinear eddy once.
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  • 98
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    Keywords: Rock failure ; fractal ; percolation ; rock modulus ; damage parameter ; rock mechanics
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    Notes: Abstract The elastic properties of a physical model representing a damaged rock matrix were studied using a square lattice deformed under tensile stress. The elastic modulusM of such a system varies in agreement with percolation theory as|x−x c | f , wherex is the damage parameter andx c the threshold value of the damage parameter,f≃3.6. Atx≃x c the scale dependence ofM can be expressed asM∼L −f/v , whereL is the size of the sample andv the correlation exponent in percolation theory. The experimental results are of interest in assessing elastic properties in earthquake focal zones and fault zones in general.
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  • 99
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    Pure and applied geophysics 134 (1990), S. 117-133 
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    Keywords: Seismic refraction ; travel times and waveforms joint inversion ; annealing algorithms
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    Notes: Abstract An algorithm of annealing is applied to a joint inversion of travel times and waveforms belonging to a synthetically generated seismic refraction experiment. The medium (crust and upper mantle) is modelled by a set of plane stratified layers and a halfspace. The obtained structure (elastic parameters and depth of layers) shows that, in spite of contaminating seismic noise and poor knowledge of the seismic source, annealing methods are a good tool in these kinds of inversion problems. We think that many characteristics of the annealing process described here could be used with real data and more sophisticated media for the crust and upper mantle of the earth than the present example.
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    Pure and applied geophysics 134 (1990), S. 195-228 
    ISSN: 1420-9136
    Keywords: Earthquakes ; coda ; source attenuation ; temporal changes ; prediction site effects
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract We analyse spectral ratio of the coda of doublets of microearthquakes. Our purpose is to find evidence for temporal changes of the attenuation in the crust before a large magnitude earthquake. A Moving Window Cross Spectral analysis of the coda of doublets gives a plot of the spectral ratio as a function of lapse time along the seismogram, for several frequency bands (SR(T, f) plot). From a certain pattern in theSR(T, f) plot, we should infer a temporal change in coda attenuation. Several doublets recorded in Central California by the USGS network are analysed. Using events very close in time from one another, we show that the radiation pattern can be different enough to induce important variations in the spectral ratio of the first arrivals and of the coda. Another doublet exhibits a strong variation of the low frequencies for stations in the region of Hollister (California), wherePhillips andAki (1986) have noted a strong amplification of low frequencies, that they attribute to site effects on unconsolidated sediments in the fault zone. These variations could be related to slight changes in local conditions (creep, or water table). On the other hand, some doublets, in the vicinity and close in time to the August 1979 Coyote Lake Earthquake (M=5.9), show no variation inSR(T, f) related to this earthquake: this proves that there was no major change in attenuation in the crust preceding this large shock. If a change occurred, it should have been confined to a very limited region, which was not sampled by the many paths we studied. The employed method probably provides today the most accurate estimation of spectral ratio in the coda of microearthquakes. It shows that there are numerous kinds of variations and that it is not straightforward to relate them to coda attenuation changes only. Also, we must be circumspect when dealing with the coda of microearthquakes in relation to forecasting earthquakes.
    Type of Medium: Electronic Resource
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