The eVect of the number of simultaneously ovipositing females on progeny sex ratio of three Homalodisca coagulata egg parasitoids, Gonatocerus ashmeadi, G. triguttatus, and G. fasciatus was investigated in the laboratory. When one female Gonatocerus parasitoid was present, progeny production was strongly female biased producing »1 male:8 females, 1:14 and 1:9 for G. ashmeadi, G. triguttatus and...

Sexual dimorphism is ubiquitous in animals and can result from selection pressure on one or both sexes. Sexual selection has become the predominant explanation for the evolution of sexual dimorphism, with strong selection on size-related mating success in males being the most common situation. The cuckoos (family Cuculidae) provide an exceptional case in which both sexes of many species are fre...

Although a negative covariance between parasite load and sexually selected trait expression is a requirement of few sexual selection models, such a covariance may be a general result of life-history allocation trade-offs. If both allocation to sexually selected traits and to somatic maintenance (immunocompetence) are condition dependent, then in populations where individuals vary in condition, ...

BACKGROUND Encyrtid secondary parasitoids of Delphacidae have not been recorded in Japan. However, they may play an important role in the rice ecosystem because they can reduce the number of Dryinidae, the natural enemies of rice planthoppers. NEW INFORMATION We found two encyrtid species, Cheiloneurus exitiosus (Perkins, 1906) and Helegonatopus dimorphus (Hoffer, 1954), from rice paddies and...

Male-biased parasitism is commonly found in higher vertebrates and is most likely to be a result of higher mobility and lower immunocompetence of male hosts than female hosts. The latter would result in higher fitness of parasites exploiting males rather than females. To test this hypothesis, we investigated foraging and reproductive performance of fleas (Xenopsylla ramesis) parasitizing male a...

struggled for years with parasites that evolve resistance to commonly used drugs. Why should it be any different in animals? Yet as far as we know, no study has ever looked at whether parasites become resistant to the chemicals in the plants that hosts use for protection, though in the Drosophila example referenced above, ethanol did not negatively affect larvae of specialist wasps as strongly ...

Palmistichus elaeisis Delvare and LaSalle (Hymenoptera: Eulophidae) is a gregarious and polyphagous parasitoid mainly of Lepidoptera pupae. The objective of this paper as to study the developent of parasitoid on Bombyx mori L. (Lepidoptera: Bombycidae) pupae exposed to one, nine, 18, 27, 36, 45 or 54 female P. elaeisis, respectively. The females of the parasitoid remained in contact with pupae ...

The absence of adaptive host responses to virulent parasites and pathogens is paradoxical. We explored the theoretical possibility that the evolution of antiparasitic egg-ejection strategies was delayed by avian hosts' lifetime experiences with brood parasitism. An analytical model indicated that individual hosts' repeated exposure to parasitism decreased the relative benefits of learning-based...

Identifying the factors used by an avian brood parasite to select host nests is important in understanding the determinates of individual reproductive success, yet such factors are poorly known for most parasitic species. Insights into these factors may come from understanding the conditions under which female parasites lay more than one egg per host nest (multiple parasitism). Using genetic te...

Social parasites exploit the colony resources of social insects. Some of them exploit the host colony as a food resource or as a shelter whereas other species also exploit the brood care behavior of their social host. Some of these species have even lost the worker caste and rely completely on the host's worker force to rear their offspring. To avoid host defenses and bypass their recognition c...