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  • 1
    Electronic Resource
    Electronic Resource
    Effect of defoliation by checkerspot caterpillars (Euphydryas phaeton) and sawfly larvae (Macrophya nigra and Tenthredo grandis) on their host plants (Chelone spp.) (1984)
    Springer
    Oecologia 63 (1984), S. 275-280 
    Details
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The effect of defoliation by herbivores, checkerspot caterpillars (Euphydryas phaeton) and sawfly larvae (Macrophya nigra and Tenthredo grandis), on the reproductive output of turtlehead (Chelone spp.) was examined. Defoliation prior to development of flower buds reduced the number of reproductive stalks, flower buds, flowers and seed capsules. Severe herbivory, after flower buds appeared, decreased the final number of seed capsules and seeds per capsule. The availability of the host plants to the herbivores was a function of prior defoliation and environmental conditions. Sawfly larvae, by defoliating the plants in midsummer, forced prediapause checkerspot caterpillars to wander in search of food plants. Decimation of these perenials by postdiapause checkerspot caterpillars in a dry spring retarded growth of turtlehead and, consequently, most of the plants were not available for egg-laying by sawflies and checkerspots.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00379889
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  • 2
    Electronic Resource
    Electronic Resource
    Effects of cages, plant age and mechanical clipping on plantain chemistry (1994)
    Springer
    Oecologia 99 (1994), S. 66-71 
    Details
    ISSN: 1432-1939
    Keywords: Cage effect ; Defoliation ; Iridoid glycosides Phenology ; Plantago lanceolata
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In plant-insect herbivore field studies, effects of cages, plant age, and mechanical clipping on host plant chemistry are often postulated but not well documented. We examined the effects of cages (for the purpose of restraining insects on experimental plots), plant age over the course of the experiment and mechanical clipping on plantain (Plantago lanceolata) chemistry. Leaf age affected the concentrations of nitrogen and iridoid glycosides (IGs; specifically aucubin and catalpol), with higher levels in newer leaves. Caged plants had higher levels of IGs and lower concentrations of nitrogen than uncaged plants. The IG concentrations were greater in new leaves of caged plants than uncaged plants, whereas the concentrations in mature leaves were unaffected by caging. Plants that were 5 weeks older had higher levels of IGs and lower nitrogen than plants harvested 5 weeks earlier. Comparison of three studies suggested that over the summer IG concentrations increase during dry years but decrease during wet years. Plants with above-ground parts clipped and then allowed to regrow for five weeks had similar concentrations of IGs and nitrogen compared to control plants; but the regrowth plants had a lower catalpol to total IG ratio. We conclude that cages and time can have significant positive effects on iridoid glycoside concentrations and significant negative effects on leaf nitrogen concentration. But our results also indicate that the direction and magnitude of the effects of cages, time and mechanical damage are not easily predicted. Therefore, it is advisable to determine and/or control for such effects in field experiments on plant-insect interactions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00317084
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  • 3
    Electronic Resource
    Electronic Resource
    Presence of predatory wasps and stinkbugs alters foraging behavior of cryptic and non-cryptic caterpillars on plantain (Plantago lanceolata) (1993)
    Springer
    Oecologia 95 (1993), S. 376-384 
    Details
    ISSN: 1432-1939
    Keywords: Predator-prey interaction ; Junonia coenia ; Spilosoma congrua ; Podisus maculiventris ; Polistes fuscatus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We examined the foraging patterns of two species of caterpillar (Junonia coenia: Nymphalidae and Spilosoma congrua: Arctiidae) that contrast in feeding specialization and crypticity on plantain (Plantago lanceolata) in the absence and presence of two different insect predators [stinkbugs, Podisus maculiventris (Pentatomidae) and wasps, Polistes fuscatus (Vespidae)]. Junonia larvae were quite apparent to human observers, feeding on upper leaf surfaces during daylight, whereas Spilosoma larvae were relatively cryptic, often hiding under leaves and in soil crevices during daylight. In the presence of either predator species, the non-cryptic Junonia caterpillars more quickly left the plant on which they were initially placed and were less apparent than Junonia larvae not exposed to predators. The presence of predators had no detectable influence on where the caterpillars occurred on the plants (new, intermediate-aged or mature leaves, or reproductive stalks). Surprisingly, the predators influenced the behavior of the inherently cryptic Spilosoma: the apparency of these larvae at night increased when wasps had access to the plots during the day. Survivorship of the non-cryptic Junonia was less than 12% when stinkbugs were present compared to 60% in their absence. Although the presence of wasps resulted in a lower relative growth rate for the non-cryptic Junonia larvae, the indirect effect of predators on reduction in survivorship due to alterations in prey growth rate through behavioral changes was less than 3%. After taking into account the decline in caterpillars per plot through predation, we found that both the amount of leaves eaten and the proportion of plants eaten were altered on plots with predators present, which suggests that the caterpillars' increased consumption countered increased maintenance costs due to the presence of predators. Overall, our results indicate that hostplant size, level of predation and type of predator can influence the degree to which these caterpillars react to the presence of insect predators. In contrast, degree of inherent feeding specialization and cryptic behavior seemed to have little effect on the expression of reactive behaviors of these caterpillars to predators.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00320992
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  • 4
    Electronic Resource
    Electronic Resource
    Foraging behavior of specialist and generalist caterpillars on plantain (Plantago lanceolata) altered by predatory stinkbugs (1992)
    Springer
    Oecologia 92 (1992), S. 596-602 
    Details
    ISSN: 1432-1939
    Keywords: Predator-prey interaction ; Foraging patterns ; Junonia coenia ; Pyrrharctia isabella ; Podisus maculiventris
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary To examine the effects of predators and plant genotype on the behavior, patterns of herbivory, growth and survivorship of caterpillars, we used an experimental garden in which we contrasted two hostplant genotypes of plantain (Plantago lanceolata), two kinds of herbivores (specialist Junonia coenia vs. generalist Pyrrharctia isabella) and two levels of caterpillar predation (with and without Podisus maculiventris stinkbugs). Each of the replicate plots per treatment contained two plants of the same genotype. The stinkbugs reduced the survivorship of the specialist caterpillars but not that of the generalists, which reflects the differences in predatoravoidance behaviors of these species. Nonetheless, the stinkbugs influenced the behavior of both caterpillar species. When stinkbugs were present, both specialist and generalist caterpillars were less likely to be found on the plant upon which they were initially placed (=“initial” plant), and they were more likely to be off both plants within the plot than larvae in the absence of predators. Consequently in the presence of the stinkbug predators, the proportion of the “initial” plants consumed was less than in the absence of the predators. Plant genotype influenced plant size and the proportion of individual plants eaten, but it did not affect larval location on the plots. Neither presence of predators nor plant genotype had an effect on relative growth rate of the caterpillars.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00317854
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  • 5
    Electronic Resource
    Electronic Resource
    Growth versus molting time of caterpillars as a function of temperature, nutrient concentration and the phenolic rutin (1990)
    Springer
    Oecologia 82 (1990), S. 107-113 
    Details
    ISSN: 1432-1939
    Keywords: Thermal conditions ; Food quality ; Growth phase ; Molt phase ; Predation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A factorial experiment tested the effects of varying nutrient concentration (normal versus diluted), presence or absence of the phenolic allelochemical rutin and daytime temperature (20, 25 and 30° C) on growth, molting and food utilization efficiencies of tobacco hornworms (Manduca sexta). Two of the utilization efficiencies (approximate digestibility and efficiency of conversion of ingested food) were unaffected by temperature; the third one, efficiency of conversion of digested food, was affected by temperature but there was no consistent effect. Lower temperatures significantly increased the proportion of the stadium spent molting, with larvae at a daytime temperature of 20° C spending 9% more of the stadium in molting than larvae at 30° C. Growth time was not influenced by nutrient concentration. When temperature was low and rutin absent, molt time and the proportion of the stadium spent molting were affected by nutrient concentration. Addition of the phenolic rutin did not have an appreciable effect on growth time or digestive processes. However, it increased molting time by 7 to 14% and thus increased the duration of the stadium and reduced relative growth rate. These results indicate that the effect of food quality on growth rate is a function of the thermal conditions of insect herbivores. At cooler temperatures, a disproportionate increase in time spent molting, rather than altered food utilization efficiencies, contributed to lower growth rates. The consequences for larval growth of fluctuating temperatures due to diurnal cycles and the presence of predators forcing larvae into thermally suboptimal microhabitats are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00318541
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  • 6
    Electronic Resource
    Electronic Resource
    Indirect effect on survivorship of caterpillars due to presence of invertebrate predators (1991)
    Springer
    Oecologia 88 (1991), S. 325-330 
    Details
    ISSN: 1432-1939
    Keywords: Predator-prey interaction ; Foraging patterns ; Hemileuca lucina ; Junonia coenia ; Podisus maculiventris
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary An indirect effects is defined here as a reduction in prey survivorship as a consequence of a reduction in growth rate of prey due to the presence of a predator that alters prey behavior. A method for partitioning the direct and indirect effects of predators on prey survivorship indicated that predatory wasps (Polistes sp.:. Vespidae) had both direct and indirect negative effects on survivorship of buckmoth caterpillars (Hemileuca lucina: Saturniidae). In a field experiment, the direct and indirect effects together accounted for 61% of the mortality of the caterpillars. A third of this reduction in survivorship due to the wasps was attributed to an indirect effect, due to the decreased growth rate of the caterpillars that moved into the interior of the hostplant to escape from the wasps. In contrast, in another field experiment, although predatory stinkbugs (Podisus maculiventris: Hemiptera) contributed to 56% of the mortality of buckeye caterpillars (Junonia coenia: Nymphalidae), the indirect effect of stinkbugs on buckeye caterpillars only accounted for 2% of the reduction in survivorship of these caterpillars. These differences in the indirect effect are discussed in particular relative to the behavior of predators and prey, ratio of predator to prey sizes, and morphology of the hostplants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00317574
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  • 7
    Electronic Resource
    Electronic Resource
    Relative susceptibility to predation of two species of caterpillar on plantain (1992)
    Springer
    Oecologia 92 (1992), S. 124-129 
    Details
    ISSN: 1432-1939
    Keywords: Junonia coenia ; Spilosoma congrua ; Podisus maculiventris ; Polistes fuscatus ; Plantago lanceolata
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The relative susceptibility to predators of a cryptic generalist caterpillar (Spilosoma congrua: Arctiidae) and a non-cryptic specialist (Junonia coenia: Nymphalidae) using the same hostplant species (Plantago lanceolata) was examined. In a laboratory experiment using predatory stinkbugs (Podisus maculiventris), more Junonia caterpillars than Spilosoma caterpillars were killed (70% vs. 16%). This result was a consequence of the Spilosoma spending some time under cover, moving frequently, feeding on leaves while under or adjacent to them, and spending little time on the leaves. In a field experiment using predatory wasps (Polistes fuscatus), the wasps found 7 times as many of the Junonia as the Spilosoma, and overall 6 times as many Junonia were killed as Spilosoma. Initially, 71% of the Junonia caterpillars encountered by wasps were killed, but by the fourth day of the test, only 22% of the Junonia encountered by wasps were killed. Over three full days of observations, a constant 50% of the Spilosoma caterpillars encountered by the wasps per day were killed. For the Junonia, evasion of predators rested on passive chemical defense. For the Spilosoma, evasion depended on being unapparent, speedy movement between feeding and resting sites and, if found, on fleeing immediately and quickly. These results indicate that Spilosoma caterpillars, by way of cryptic and escape behaviors, can be less susceptible to insect predators than Junonia caterpillars.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00317272
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  • 8
    Electronic Resource
    Electronic Resource
    Simultaneous effects of night-time temperature and an allelochemical on performance of an insect herbivore (1995)
    Springer
    Oecologia 104 (1995), S. 225-233 
    Details
    ISSN: 1432-1939
    Keywords: Development ; Global warming ; Nutritional ecology ; Plant-herbivore interactions ; Rutin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract One effect of global warming may be an increase in night-time temperatures with daytime temperatures remaining largely unchanged. We examined this potential effect of global warming on the performance of tobacco hornworm larvae, Manduca sexta (Sphingidae), by manipulating night-time temperature and dietary rutin levels simultaneously under a 12 light:12 dark photoregime. All four thermal regimes (26:14, 26:18, 26:22, and 26:26° C) had a daytime temperature of 26° C, with the night-time temperature increased from 14 to 26° C by increments of 4° C. Dietary rutin levels (0, 10 and 20 μmoles g−1 fresh weight of diet) reflected those occurring naturally in the leaves of tomato, a preferred host plant of M. sexta. With low night-time temperatures (14 and 18° C), rutin had a negative linear effect on developmental rate, relative growth rate and relative consumption rate of the caterpillars. However, at a night-time temperature of 22° C, rutin had a negative non-linear effect. At a night-time temperature of 26° C, rutin had a negative linear impact but less so than at the other nightime temperatures. Likewise, the negative effect of rutin on molting duration was mitigated as night-time temperature increased. Final larval weight decreased linearly with increased dietary rutin concentrations. Total amount of food ingested was not affected by either rutin or thermal regime. As expected, the caterpillars developed faster under an alternating 26:14° C regime than a constant 20° C regime (the average temperature for the alternating regime), but the effect of rutin depended on the thermal regime. Switching daytime and night-time temperatures had no statistically significant effect on caterpillar performance. Overall, the effect of rutin on rates of larval performance was greater at some levels of warmer nights but damped at another level. These results indicate that the potential effect of warmer nights on insect performance is not a simple function of temperature because there can be interactions between night-time temperature and dietary allelochemicals.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00328587
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  • 9
    Electronic Resource
    Electronic Resource
    Resource availability and the trichome defenses of tomato plants (1996)
    Springer
    Oecologia 106 (1996), S. 181-191 
    Details
    ISSN: 1432-1939
    Keywords: Trichome ; Growth-differentiation balance ; Carbon-nutrient balance ; Lycopersicon esculentum ; Manduca sexta
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We conducted two experiments to determine how resource availability influenced allocation by tomato (Lycopersicon esculentum) to trichomes, and how different patterns of trichome allocation by plants grown in different resource environments might then influence the behavior of tobacco hornworm (Manduca sexta) caterpillars. In the first experiment we used high and low levels of light and water, and then, using scanning electron microscopy, determined trichome densities on the leaves and stems. We sampled leaves and stems at several places throughout the plant to determine whether there were within-plant differences in allocation to trichomes. The results of the first experiment showed that resource availability influenced allocation to trichome growth. Patterns in high and low-light supported both the growth-differentiation balance hypothesis (GDBH) and the carbon-nutrient balance hypothesis (CNBH). However, the GDBH was not supported by differences among water treatments. Contrary, to predictions of the GDBH, plants with intermediate growth did not have the highest trichome densities, and plants with similar growth differed in trichome density. Possible biological and artifactual explanations are discussed. The first experiment also showed that there was within-plant variation in allocation to trichomes, and that plant resource availability may influence within-plant variation in allocation to trichomes. In the second experiment, we grew plants in high and low-light, and then monitored the behavior of tobacco hornworms on the stems of these plants in the laboratory. This experiment demonstrated that the light environment that tomato plants were grown in influenced the resting behavior of caterpillars. Furthermore, it demonstrated that both glandular and non-glandular trichomes impeded caterpillars from searching for food. Overall, this study indicated that plant resource availability can influence allocation to trichome defenses, and that these differences may affect insect herbivores.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00328597
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  • 10
    Electronic Resource
    Electronic Resource
    Effect of group size on parasitism in a natural population of the Baltimore checkerspot Euphydryas phaeton (1981)
    Springer
    Oecologia 49 (1981), S. 201-206 
    Details
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The effect of group size of early instars on parasitism of Euphydryas phaeton (Nymphalidae) was examined. Different numbers of larvae were stocked per web to determine the effect of group size on parasitism. Larval aggregations of moderate size (the size occurring naturally) had the least parasitism. Larger larval groups had a disproportionately high rate of parasitism. The major larval parasitoids located vulnerable larvae within webs, instead of attacking larvae available on the outside of webs. Parasitism rates were similar for larvae of damaged and undamaged webs, a consequence of the behavior and location of larvae in the webs. Lower limit to group size was a function of facilitation of larval numbers in reaching the first feeding site, the top of the host plant. Feeding facilitation by larval aggregations was not a factor in larval survival or growth.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00349188
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