bluuebunny/crossref_metadata_2025_split huggingface dataset:
The use of kairomones for foraging decisions by an aphid parasitoid in small host aggregations
Authors: SHALTIEL LIORA , AYAL YORAM 
Published: March 2003

1. The wasp Diaeretiella rapae uses honeydew emitted by its host, the cabbage aphid Brevicoryne brassica, as a kairomone (chemicals emitted by an organism as part of its activity and used by its natural enemies to their advantage). The role of the kairomone in foraging decisions by the parasitic wasp was explored by manipulating the amount of honeydew and the number of aphids in a colony independently. The count‐down patch‐exploitation mechanism (Iwasa et al., 1981) was employed to predict the results of these manipulations and contrast them with the predictions of Waage's (1979) model.2. Kairomonal activity of honeydew decreased as the honeydew aged and lost its activity completely within 72 h.3. The wasp was exposed to different amounts of honeydew on (a) aphid‐free leaves and (b) leaves bearing colonies of 150 aphids. The parasitoid search time on both leaf types increased with increasing honeydew contamination. On aphid‐bearing leaves, the number of attacked aphids in the colonies also increased with increasing honeydew contamination. The presence of aphids reduced the parasitoid search time compared to search time on aphid‐bearing leaves with the same level of honeydew contamination, as predicted by the count‐down model.4. Parasitoids exposed to the same amount of honeydew, but a different number of aphids in a colony on the leaf, first increased the number of aphids attacked in relation to the number of aphids in the colony. But as the colony reached a certain size, the number of aphids attacked levelled off, despite the increase in the number of aphids in the colony. Search time was variable but did not exhibit any trend as the number of aphids in the colonies increased.5. These results suggest that honeydew level is used by D. rapae as a cue for assessment of the number of aphids in the colony. In such cases, a count‐down exploitation mechanism gives the best results to a forager. Many parasitoids may use kairomones for patch assessment and will therefore employ a count‐down rule during patch exploitation.
Influence of host plant vs. natural enemies on the spatial distribution of a pine sawfly,Neodiprion autumnalis
Authors: Mcmillin Joel. D. , Wagner Michael R. 
Published: March 2003

Abstract.1. The pine sawfly,Neodiprion autumnalis, infests ponderosa pine,Pinus ponderosa, growing at low densities near the bottom of an altitudinal gradient in Arizona, U.S.A. The relative importance of host‐plant quality vs. natural‐enemy effects in determining the spatial distribution of this sawfly was examined over a 3‐year period.2. Field and laboratory bioassays were conducted on all life stages ofN. autumnalisat two forest stand densities (high ≥ 23 m2ha–1, low ≤ 7 m2ha–1) and at two elevations (bottom slope = 2390 m, top slope = 2540 m). These experiments were used for constructing life tables ofN. autumnalisthat compared the effects of host‐plant quality on oviposition preference and progeny performance with the effects of natural enemies at different tree densities and elevations.3. Life‐table analyses determined that mortality attributed to host‐plant effects during the egg and larval stages had the largest impact on fitness between tree densities and elevations.4. Natural enemies caused a significant reduction in progeny survival, but their effects were similar across all tree densities and elevations during egg and larval life stages. However, cocoon‐stage survival did vary between tree densities and elevations due to natural‐enemy effects.5. It was concluded that the observed oviposition preference for, and higher progeny performance on, trees at low densities and bottom slope elevations were caused primarily by host‐plant effects.6. These results further the argument that heterogeneity at the resource level (i.e. bottom‐up forces) determines potential outcomes of multitrophic level interactions.
Desiccation tolerance and starvation resistance exhibit opposite latitudinal clines in Indian geographical populations of Drosophila kikkawai
Authors: Karan Dev. , Parkash Ravi. 
Published: March 2003

Abstract.1. Desiccation tolerance and starvation resistance demonstrated significant differentiation among seven Indian geographical populations of Drosophila kikkawai, collected along a latitudinal range of 12.6–32.7 °N. Lack of significant differences in two successive generations suggested that these physiological traits were genetically controlled.2. North Indian populations of D. kikkawai displayed significantly higher desiccation tolerance than southern populations, whereas there was a reverse trend for starvation tolerance (r > 0.90). Regression slope values indicated an increase of 0.61 h for desiccation and a decrease of 1.71 h per degree latitude for starvation tolerance at 17 °C. The traits evidenced opposite latitudinal clines, and such data also matched thermal climatic conditions on the Indian subcontinent. The survival duration for such traits was significantly higher at 17 than at 25 °C.3. Significantly higher starvation tolerance in south Indian populations might be due to large population size, species interactions, and higher metabolic rates in the humid tropical environments. In contrast, prolonged unfavourable colder climatic conditions are known to favour starvation tolerance in temperate regions. Thus, the causes of desiccation and starvation tolerance seem quite different under tropical and temperate conditions.4. Starvation tolerance was correlated negatively with body weight and ovariole number, which might be due to a trade‐off in favour of greater allocation to non‐lipidic reserves for sustaining starvation tolerance in the tropics. Reduction in metabolic rate may not be applicable for observed higher starvation tolerance in the tropical populations.5. Multiple regression analysis demonstrated a major effect of coefficient of variation of mean monthly temperature for both the traits of ecological significance. Thus, Indian geographical populations of D. kikkawai provided evidence of independent genetic divergence for starvation and desiccation tolerance under natural conditions.
Foraging in yellow dung flies: testing for a small‐male time budget advantage
Authors: Blanckenhorn WolF. U. , Viele StuD. N. T. 
Published: March 2003

Summary1. Mating and foraging are generally mutually exclusive activities. Individuals are thus faced with a continuous trade‐off between time and energy expended in foraging and mating, but different phenotypes should respond to this trade‐off in different ways.2. Sexual selection theory predicts that females should maximize their time and energy spent gathering resources, whereas males should maximize their time and energy spent obtaining mates, thus minimizing their time spent foraging, subject to the constraint that they need to forage minimally to sustain their activity.3. Smaller individuals require less food to maintain their activity. Small males in particular could therefore increase mating effort at the expense of foraging effort and, all else being equal, may thus enjoy a time budget advantage relative to large males. On the other hand, larger individuals may compensate by being more efficient at finding prey and/or extracting nutrients.4. The effects of sex, body size, and prey density on foraging time budgets of male and female yellow dung flies, Scathophaga stercoraria, were investigated in the laboratory.5. Higher prey density (Drosophila melanogaster) resulted in reduced feeding (= handling) and hunting (= waiting or search) times for both sexes, as predicted by the marginal value theorem applied to foraging theory. Females fed longer on a prey item than did males, and also caught the next prey item more quickly. Large individuals extracted nutrients more quickly, but were not faster at catching prey. Small individuals satiated more quickly than larger individuals and also ate fewer prey items.6. These results are largely consistent with the predictions and suggest a small‐male time budget advantage in the yellow dung fly. Integrating the various predictions to test directly for a small‐male time budget advantage is difficult in the laboratory, however, because hunting times are unlikely to reflect the natural situation. To what extent these results lead to increased probabilities for small males of obtaining matings in the field remains to be demonstrated.
Flexible larval development and the timing of destructive feeding by a solitary endoparasitoid: an optimal foraging problem in evolutionary perspective
Authors: Hemerik LiA. , Harvey Jeffrey A. 
Published: March 2003

Summary1. In studying the evolution of life‐history strategies in parasitoids, considerable attention has been paid to the relationship between host quality and parasitoid fitness. Various workers have reported that host quality influences parasitoid size, development time, and survival. Because body size is frequently correlated with fecundity, longevity, and host‐finding ability in parasitoids, this parameter is usually considered to be the main target of selection.2. In koinobiont parasitoids that consume the entire host before pupation, adult parasitoid size and development time are often strongly correlated with host size at the time when it is developmentally arrested through destructive feeding by the parasitoid larva.3. Here, a mathematical model is proposed to describe the larval feeding behaviour of the solitary koinobiont endoparasitoid Venturia canescens in four larval stadia of its host Plodia interpunctella. In particular, the model describes how adult size, represented by an exponential growth rate, and development time are traded off when the parasitoid develops in nutritionally suboptimal second stadium hosts.4. Using a graphical model, the different conditions faced by V. canescens during development in various host species of greatly differing mass are illustrated.5. It is argued that the relative importance of size and development time on parasitoid fitness is determined by ecological and biological characteristics of both host and parasitoid, and it is suggested that there may be correlations between life‐history traits and host‐utilisation strategies among koinobionts.
Effects of phytochemical variation in quaking aspen Populus tremuloides clones on gypsy moth Lymantria dispar performance in the field and laboratory
Authors: Osier Tod L. , Hwang Shaw‐Y. , Lindroth Richard L. 
Published: March 2003

Summary1. This study investigated how phytochemical variation among clones of quaking aspen Populus tremuloides, growing in a common habitat, affects the growth and fecundity of a model herbivore.2. Gypsy moth Lymantria dispar larvae were reared from egg hatch to pupation on 10 aspen clones in the field or on excised foliage in the laboratory. Foliage was collected from each clone, and concentrations of phenolic glycosides, condensed tannins, nitrogen, and water were determined.3. Herbivore fitness parameters and aspen phytochemical concentrations varied significantly among clones. In both the field and laboratory, larvae reared on clones containing high concentrations of phenolic glycosides exhibited prolonged developmental times and reduced pupal weights and fecundity. Herbivore performance parameters were also related positively to foliar nitrogen concentrations in the laboratory. Food consumption, but neither growth nor reproductive parameters, were related positively to condensed tannin concentrations.4. In this study, foliar concentrations of phenolic glycosides were implicated as a significant determinant of food quality for gypsy moths, consistent with results of previous laboratory experiments. Additionally, this study documents a case in which host plant variation at a local level influences the performance and possibly the distribution and abundance of an important herbivore.
The size–distance relationship in the wood ant Formica rufa
Authors: Wright Philip J. , Bonser Robert , Chukwu Uchegbu O. 
Published: March 2003

Summary1. The size–distance relationship among honeydew‐collecting foragers of the red wood ant Formica rufa was investigated. Within the colony territory, the size (as measured by head width) and fresh weight of samples of foragers were determined for ants ascending and descending trees near, and farther from, the central nest mound.2. The mean size of the ants was significantly higher at far trees than at near trees in six out of the seven colonies investigated, confirming the general presence of the size–distance relationship.3. In three colonies, a load–distance relationship was also found. For a given head width, honeydew‐carrying ants descending far trees were significantly heavier than those descending near trees (i.e. they were carrying heavier loads from trees farther away from the central nest mound).4. This is the first time that both load–distance and size–distance relationships have been reported in foraging workers from the same ant colony.5. The combined effects of these characteristics suggest that colony foraging efficiency is enhanced by far trees being visited by the larger workers that then return with heavier loads of honeydew.
Diet and size influence sexual advertisement and copulatory success of males in Mediterranean fruit fly leks
Authors: Kaspi Roy , Taylor Phillip W. , Yuval Boaz 
Published: March 2003

Summary1. The objective of the work reported here was to test the hypothesis that in insects that invest considerable energy in sexual displays and courtship, foraging successfully for food affects their subsequent performance and copulatory success in leks. Accordingly, the interactions between body size and diet on initiation of lekking behaviour and copulatory success in male Mediterranean fruit flies Ceratitis capitata (Diptera: Tephritidae) were investigated.2. Protein‐fed males were heavier and contained more protein and less lipid reserves than protein‐deprived males. Protein‐fed males were more likely to emit pheromone in leks and, consequently, were more likely to copulate than protein‐deprived males. Furthermore, protein‐fed males tended to start calling earlier than their nutritionally deprived competitors.3. Though size was not related to initiation of lek behaviour, large males were more likely to copulate than small males. Among protein‐fed males, large individuals tended to mate earlier than smaller individuals.4. Generally, in lek mating systems where a considerable investment of time and energy is required by males, foraging successfully for nutritional resources prior to engaging in territorial or courtship behaviour is essential for reproductive success.
Insect colonisation sequences in bracts of Heliconia caribaea in Puerto Rico
Authors: Richardson Barbara A. , Hull Gillian A. 
Published: March 2003

Summary1. It was predicted that insects colonising Heliconia phytotelmata would exploit the different bract conditions along inflorescences, which result from sequential ageing.2. Flowering of H. caribaea is asynchronous over a 6‐month period. A method of identifying bracts of the same age, regardless of position on the inflorescence or inflorescence age, and from different plants over 2 years, was developed using comparative flowering phenology.3. Heliconia insect larval communities were remarkably consistent from year to year in species composition and relative abundance. Occurrence within the plant population was also similar from year to year, and most species were Heliconia specific.4. Significant interspecific differences were found in bract utilisation, with populations peaking at different stages of bract development. Ceratopogonid larvae were the earliest colonisers, followed by psychodids, syrphids, and culicids. Tipulids occurred much later in the cycle of bract development and ageing. These patterns were consistent in both years.5. Patterns of bract utilisation provide strong support for temporal niche partitioning by variation in oviposition and development time. Communities were not considered to be structured by predation or pH changes along the bract sequence.
Male pioneering as a mating strategy: the case of the beetle Maladera matrida
Authors: Harari Ally R. , Ben‐Yakir David , Rosen David 
Published: March 2003

Summary1. The phenomenon of male pioneering, whereby males are active (daily) before females, is compared with protandry, a phenomenon whereby males are sexually matured before females. The effects of natural selection and sexual selection on both phenomena are discussed.2. In Maladera matrida Argaman (Coleoptera: Scarabaeidae), males emerged from the soil a few minutes before females, every evening, to feed and mate.3. Aggregations of males and females are formed at sites of plant damage where males initiated feeding.4. All copulations were initiated at the beginning of the activity period so males that emerge earlier may increase their probability of finding a mate.5. Females mate only once in an evening.6. Males that emerge later may not find receptive females with which to mate.7. The aggregation of beetles per se did not contribute to the individual mating success because it occurred during and after the copulating had begun.8. Male pioneering may evolve through sexual selection by means of male–male competition in time to achieve receptive females.
Reduced flight capability in British Virgin Island populations of a wing‐dimorphic insect: the role of habitat isolation, persistence, and structure
Authors: Denno Robert F. , Hawthorne David J. , Thorne Barbara L. , Gratton Claudio 
Published: March 2003

Summary1. The effects of habitat isolation, persistence, and host‐plant structure on the incidence of dispersal capability (per cent macroptery) in populations of the delphacid planthopper Toya venilia were examined throughout the British Virgin Islands. The host plant of this delphacid is salt grass Sporobolus virginicus, which grows either in undisturbed habitats (large expanses on intertidal salt flats and around the margins of salt ponds, or small patches of sparse vegetation on sand dunes along the shore), or in less persistent, disturbed habitats (managed lawns).2. Both sexes of T. venilia were significantly more macropterous in disturbed habitats (77.1% in males, 12.5% in females) than in more persistent, undisturbed habitats (19.2% in males, < 1% in females).3. Males exhibited significantly higher levels of macroptery (26.9 ± 7.6%) than did females (2.0 ± 1.7%), and per cent macroptery was positively density dependent for both sexes in field populations.4. There was no evidence that the low incidence of female macroptery in a subset of island populations inhabiting natural habitats (1.7 ± 1.2%) was attributable to the effects of isolation on oceanic islands. The incidence of macroptery in British Virgin Island populations of T. venilia was not different from that observed in mainland delphacid species existing in habitats of similar duration.5. Rather, the persistence of most salt grass habitats throughout the British Virgin Islands best explains the evolution of flight reduction in females of this island‐inhabiting delphacid.6. Males were significantly more macropterous in populations occupying dune vegetation (37.6 ± 9.8%) than in populations occupying salt flat–pond margin habitats (7.6 ± 5.6%). By contrast, females exhibited low levels of macroptery in both dune (0%) and salt flat–pond margin (< 1%) habitats. Variation in salt‐grass structure probably underlies this habitat‐related difference in macroptery because flight‐capable males of planthoppers are better able to locate females in the sparse‐structured grass growing on dunes. This habitat‐related difference in male macroptery accounted for the generally higher level of macroptery observed in males than in females throughout the islands.7. The importance of habitat persistence and structure in explaining the incidence of dispersal capability in T. venilia is probably indicative of the key role these two factors play in shaping the dispersal strategies of many insects.
Changes in abundance of Vespula germanica and V. vulgaris in England
Authors: Archer Michael E. 
Published: March 2003

Summary1. Thirteen time series, varying from 17 to 27 years, of the abundance of Vespula germanica and V. vulgaris from lowland England are examined. The time series depend on either spring queens and workers taken in Malaise or suction traps, or collected colonies.2. During the late 1970s and early 1980s, the abundance of V. germanica declined abruptly but that of V. vulgaris did not.3. During the early 1980s, the 2‐year cycle of annual abundance of V. vulgaris changed to a nearly perfectly damped pattern of annual abundances.4. The most likely factor causing these population changes was the increased use of pesticides acting directly by killing the wasps and indirectly by reducing their food resources.5. The difference in response of the two species to increased pesticide use may be related to a difference in foraging ability.
Macrogeographic clines in fecundity, reproductive allocation, and offspring size of the forest tent caterpillar Malacosoma disstria
Authors: Parry Dylan , Goyer Richard A. , Lenhard Gerald J. 
Published: March 2003

Summary1. The fecundity of the forest tent caterpillar varies considerably across its geographic range. Field data indicate that populations in the southern United States (Gulf States) produce nearly twice as many eggs as females from Canada or the Lake States, with little or no difference in the size of adult females.2. In controlled rearing experiments, female forest tent caterpillar from the southern United States (Louisiana) had much larger clutch sizes than same sized females from northern populations in Michigan or Manitoba, Canada. Increased fecundity in Louisiana females was achieved through a significant reduction in egg size and a concomitant increase in the allocation of resources to egg production.3. Comparison of 10 forest tent caterpillar populations spanning a 27° latitudinal gradient, validated the results of detailed comparisons among the three populations above by confirming the strong negative correlation between latitude and clutch size.4. Neonate forest tent caterpillars from Manitoba were significantly larger than larvae from either Michigan or Louisiana. Michigan larvae were intermediate in size. It is postulated that large neonates are advantageous in thermally limiting environments. More than three times as many degree‐days are available to Louisiana neonates during the first 2 weeks after hatching. A consistently favourable climate during the vulnerable post‐hatching period may have allowed the evolution of larger clutches at the expense of neonate size in southern populations.