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  • Springer  (271)
  • Wiley  (110)
  • Springer Nature  (72)
  • American Geophysical Union  (32)
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Colloid & polymer science 163 (1959), S. 149-150 
    ISSN: 1435-1536
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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  • 2
    ISSN: 1570-7458
    Keywords: Rhopalosiphum maidis ; Zea mays ; induced plant volatiles ; repellence ; (E)-β-farnesene ; alarm pheromone ; plant insect interactions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract When maize plants, Zea mays L., are mechanically damaged and the damaged sites are treated with caterpillar regurgitant, the plants will release a specific blend of volatiles. It is known that these volatiles can be attractive to natural enemies of herbivores. We hypothesise that the plant volatiles constitute part of the induced plant defence and that herbivores will be affected by the odours as well. In laboratory and semi-field studies this hypothesis was tested for the aphid Rhopalosiphum maidis (Fitch) (Rhynchota, Sternorrhyncha, Aphididae). In a Y-tube olfactometer significantly more aphids chose the odour of healthy, undamaged maize seedlings when tested against clean air or plants treated with regurgitant. Clean air was chosen more often when tested next to the odour of treated plants. This apparently repellent effect of the odour of treated plants was significant for winged aphids, but not for the wingless aphids. In field experiments aphids were released in the centre of circles of eight potted maize plants. Four plants in each circle were damaged and treated with caterpillar regurgitant while the other plants were left unharmed. At different intervals after aphid release, the number of aphids was counted on each plant. Significantly fewer winged and wingless aphids were found back on treated plants than on healthy plants. We suggest that herbivores may be repelled by the odours because they could indicate that: 1) the plant has initiated the production of toxic compounds; 2) potential competitors are present on the plant; 3) the plant is attractive to parasitoids and predators. Aphids may be particularly sensitive to induced maize volatiles because one of the major compounds emitted by the plant is (E)-β-farnesene, which is a common alarm pheromone for aphids. Collections and analyses of the odours emitted by crushed R. maidis confirmed that it too emits (E)-β-farnesene when stressed. The results are discussed in context of plant defence strategies and their possible exploitation for the control of pest insects.
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Entomologia experimentalis et applicata 84 (1997), S. 85-92 
    ISSN: 1570-7458
    Keywords: Coccinellids ; Hyperaspis notata ; life table statistics ; insect development ; intrinsic rates of increase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The coccinellid Hyperaspis notata Mulsant was introduced into Africa for the biological control of the cassava mealybug, Phenacoccus manihoti Matile-Ferrero. Two cohorts of strains, one originating from Southern Brazil and Paraguay feeding on P. manihoti, and one from Colombia feeding on Phenacoccus herreni Cox & Williams were studied at different temperatures between 15 and 34 °C and age-specific life tables were constructed. Although in the areas of origin the climatical conditions and the food sources are different, the survivorship and developmental times at the same temperature differed little among the two strains, the Colombian strain being slightly more tolerant to high temperatures. Jacknife estimates of the intrinsic rates of increase (rm) peaked very close to 30 °C for the two strains.
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Entomologia experimentalis et applicata 85 (1997), S. 169-175 
    ISSN: 1570-7458
    Keywords: Cydia pomonella ; Lepidoptera ; Tortricidae ; flight distance ; dispersal ; flight mill ; heritability ; colonisation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Cydia pomonella L. (Lepidoptera: Tortricidae) is considered to be rather sedentary, but some individuals undertake flights of several kilometres in the field. This paper investigates the genetic influence on this variability. The flight capacity was measured in the laboratory by a flight mill and its heritability was estimated for two different strains. The laboratory strain was kept for more than 45 generations and the field strain from Embrach (northern Switzerland) was recently collected in the field. The multiple-trait-restricted-maximum-likelihood method was used for the estimation of genetic variances and covariances. A mixed full-sib/half-sib design was applied for the field strain and a full-sib design for the laboratory strain. The heritability of total distance was 0.57 for the field strain and 0.37 for the laboratory strain (both sexes). In addition, a heritability of 0.38 for total distance was estimated by parent-offspring regression for the laboratory strain. All three values were significantly different from zero P〈0.05 and show that there is a significant additive genetic influence on flight capacity. The genetic correlations between total distance and other flight traits (total duration, flight velocity, longest flight) were between 0.84 and 1.00 for both strains and suggest that these traits actually belong to a single one. High genetic correlations were also found between total distance and the morphological traits body weight and wing length for the field strain, whereas a negative correlation was found between total flight distance and body weight for the laboratory strain. This difference between the two strains was interpreted as a possible trade-off between flight capacity and fecundity.
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Entomologia experimentalis et applicata 88 (1998), S. 49-58 
    ISSN: 1570-7458
    Keywords: Pieris brassicae ; Cotesia glomerata ; parasitoid ; hemocytes ; inhibition of encapsulation ; development
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Cotesia glomerata L. (Hymenoptera: Braconidae) is a parasitoid of early instar larvae of Pieris brassicae L. (Lepidoptera: Pieridae). Late instars of P. brassicae can more often overcome parasitization by hemocytic encapsulation of C. glomerata eggs. Short-term hemocyte responses to parasitization were examined in third and fourth instar larvae of P. brassicae. Total and differential hemocyte counts did not differ between parasitized and unparasitized host larvae. A rapid, but temporary decrease of total hemocyte as well as plasmatocyte numbers was observed immediately after oviposition. Numbers of hemocytes adhering to tissues were shown to be the same in untreated, wounded and parasitized P. brassicae larvae by tracing hemocytes with monoclonal antibodies as markers. The in vitro spreading ability of hemocytes from unparasitized third and fourth instar larvae was lower than that of the last instar's; parasitization, however, had no influence on hemocyte spreading. We therefore suggest that the higher parasitization success of C. glomerata in earlier instars of P. brassicae is mainly due to the low spreading ability of the hemocytes. Abbreviations: ACS – anticoagulant saline; BSA – bovine serum albumin; DABCO – 1,4-diazabicyclo-[2,2,2]-octane; DHC – differential hemocyte count; FITC – fluorescein isothiocyanate; GR – granular cells; LPS – lipopolysaccharide; mAb – monoclonal antibody; OE – oenocytoids; PL – plasmatocytes; PRO – prohemocytes; PS – Pieris saline; PVP – polyvinylpyrrolidone; TBS – tris-buffered saline; THC – total hemocyte count.
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Entomologia experimentalis et applicata 96 (2000), S. 213-219 
    ISSN: 1570-7458
    Keywords: herbivore ; host finding ; olfactometer ; volatiles ; oviposition ; discrimination ; Coleoptera ; Bruchidae ; pest control
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We studied the response of female Callosobruchus chinensis to chemical cues emitted by cowpea seeds at different stages of bruchid infestation (uninfested, egg carrying, L1-, and L4-infested). Olfactory attractiveness was determined in Y-tube olfactometer assays by testing individual seed categories against either clean air or uninfested seeds. Oviposition preferences between uninfested and infested seeds were determined in petri-dish choice-experiments. The olfactometer assays revealed that weevils discriminate between seeds containing different stages of developing bruchids on the basis of olfactory cues. While odors from uninfested and egg-carrying seeds acted as attractants, odors from L1- and L4-infested seeds failed to induce a positive response by the bruchids. When given a choice between uninfested and infested seeds in the olfactometer, weevils preferred uninfested seeds over L1- and L4-infested seeds, but failed to distinguish between uninfested and egg-carrying seeds. In the oviposition experiment as well, bruchids showed a distinct preference for uninfested seeds when offered in combination with L1- and L4-infested seeds. This experiment further showed a reduced acceptance of egg carrying seeds. Our results indicate that C. chinensis females use chemical information during both host searching and host acceptance. Volatiles from uninfested or egg carrying seeds act as attractants, while deterrence increases as development of bruchid immature stages progresses.
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Entomologia experimentalis et applicata 88 (1998), S. 97-99 
    ISSN: 1570-7458
    Keywords: Coleoptera ; Curculionidae ; Anthonomus pomorum ; temperature ; diapause ; flight behavior
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Entomologia experimentalis et applicata 94 (2000), S. 123-132 
    ISSN: 1570-7458
    Keywords: Pholetesor bicolor ; Phyllonorycter pomonella ; leafminer ; host selection ; host location ; learning ; oviposition ; parasitoid
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The relationship between host stage selection and foraging behaviour of Pholetesor bicolor Nees (Hymenoptera: Braconidae), a larval parasitoid of Phyllonorycter spp. (Lepidoptera: Gracillariidae), was investigated under laboratory conditions. The endophytic host develops through two larval stages with different feeding habits, accordingly named sap- and tissue-feeders. The parasitoid was able to find and parasitise both larval stages, even though it is most successful in parasitising the sap-feeder stage. The influence of experience in the parasitoid's searching behaviour was observed in a choice bioassay. Searching activity increased when either contact experience with the sap- or the tissue-feeder host was given. Furthermore, the ability of the parasitoid to locate a sap- or a tissue-feeder infested plant was influenced by the type of experience given prior to the bioassay. Naive females were less active, and were observed with equal frequency on sap-feeder, tissue-feeder and non-infested plants. In contrast, females that were given previous contact experience with sap-feeders (i.e., the host stage which provided the most successful parasitism) were observed foraging more often on plants infested by the sap-feeders, than on those infested by tissue-feeders or on non-infested plants. Experience with a tissue-feeder host had no detectable effect on host stage location and only enhanced P. bicolor's foraging activity. The advantages of learning in this tritrophic system are discussed.
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Entomologia experimentalis et applicata 92 (1999), S. 63-72 
    ISSN: 1570-7458
    Keywords: Cydia pomonella ; α-farnesene ; host plant finding ; sexual dimorphism ; mating status ; dose-response
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The role of host plant-derived volatile substances on the behaviour of adult codling moth, Cydia pomonella L. (Lepidoptera: Tortricidae) is poorly understood. We tested the response of females and males to a range of α-farnesene dosages. Natural α-farnesene from apples contains the E,E and Z,E isomers in varying proportions. No difference in the response of C. pomonella to preparations containing two different proportions of the E,E and Z,E isomers was noted (77:20.7 or 1.2:84.7% E,E and Z,E isomers respectively), indicating a similar bioactivity of E,E and Z,E α-farnesene on codling moth. A marked sexual dimorphism was found to increasing dosages of α-farnesene. Females were attracted to low dosages (starting from 63.4 ng) and repelled by high dosages (ending at 12 688 ng). The dose response over this concentration range was linear with a negative slope. Both mated and virgin females responded similarly in kind but differently in degree, both attraction and repellency being more pronounced in mated females. Males were neither attracted nor repelled over a large dose range (63.4 to 12 688 ng) except the highest rate which was attractive. This indicates a stronger dependency of females on plant-derived volatiles.
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  • 10
    ISSN: 1570-7458
    Keywords: parasitoid ; Aenasius vexans ; Encyrtidae ; sex allocation ; sex ratio ; preference ; host size ; koinobiont ; biological control
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The solitary endoparasitoid Aenasius vexans Kerrich (Hymenoptera: Encyrtidae) is used for augmentative releases against the cassava mealybug, Phenacoccus herreni Cox & Williams (Sternorrhyncha: Pseudococcidae), an important pest on cassava in South America. In light of the need for large numbers of high quality females, experiments were conducted on host stage suitability and sex allocation. In choice and no-choice experiments, individual female wasps were offered second and third instar, as well as adult, hosts. During the first five days after emergence, the wasps showed a steady increase in the number of hosts they successfully parasitised per day, but the respective secondary sex ratio for each instar remained constant. Parasitism was highest for third instar hosts in no-choice tests, while in choice tests parasitism was highest in both third instars and adults. The later the developmental stage of the host at oviposition, the faster the parasitoids developed and emerged, and for each host stage, the development time of males was shorter than for females. The sex ratio of the wasps emerging from hosts that were parasitised as second instars was strongly male-biased, while the apparently preferred later stages yielded significantly more females than males. Female and male A. vexans emerging from hosts parasitised at the third instar were significantly larger than for the other stages. This may explain the preference for the third instar as well as the female-biased sex ratio, as size is usually positively correlated with higher fitness, especially in females. The results suggest that third instar hosts are the most suitable for rearing high numbers of large females.
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