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International audience; Although animal contests for resources are often settled in favour of individuals with the greatest fighting abilities, other factors, such as those affecting the value that contestants place on the resource, can also influence contest resolution and aggressiveness. For example, competitors should fight more fiercely for access to larger than smaller food items. However, this also depends on contestants' subjective value of the resource: individuals deprived of a given resource should value it more highly than individuals that recently had access to it. They should therefore be more aggressive and win contests more frequently. In some parasitoid species, adult females fight for hosts on which to lay eggs and feed. Using the parasitoid Eupelmus vuilleti, we investigated the effect on contest outcome of two factors affecting females' subjective host value: the quality of the habitat previously encountered by females (either rich or poor in hosts) and females' physiological state (i.e. the number of ready-to-lay eggs in their ovaries). Subjective host value should increase with both host scarcity and egg load.We first described the agonistic behaviours displayed by E. vuilleti females during contests and then verified that difference in habitat quality was perceived by females (they modified their host exploitation behaviours accordingly) but did not affect their egg load, so that the effects of both factors could be separated. Both habitat quality experience and egg load affected contest outcomes, with egg load asymmetry being the main factor in this species. Our results support game theoretical predictions.

Callosobruchus maculatus (F.) (Coleoptera : Bruchidae) is a tropical beetle that develops in the seeds of Vigna unguiculata. C. maculatus adults show an imaginal polymorphism with differences in morphological, behavioral and reproductive characteristics. Adults of the flight morph that emerge in cowpea storage systems were studied under natural climatic conditions. A large number of the flight morph females were in reproductive diapause and had a long imaginal life. These females did not synthesize vitellogenin, produced a specific diapause protein and possessed significant protein reserves. This suggests that the beetles survived in the tropical ecosystem for a long time and colonized the crops during the cowpea growing and flowering phases. Analysis of reproductive activity in females captured in the V. unguiculata crops indicates that they terminated their reproductive diapause and began to lay eggs as soon as the pods were formed. Few females of the flight morph were sexually active at the beginning of imaginal life. In this paper we discuss the adaptive significance of these two reproductive strategies in females of C. maculatus.

The development of populations of two species of bruchids, B. atrolineatus and C. maculatus, in traditional stores containing cowpea pods was analysed in the Niamey area of Niger. At the beginning of the storage period, the first generation of B. atrolineatus adults is sexually active, mates and oviposits on the pods. Later, as the population increases dramatically, there is a correspondingly higher percentage of adults exhibiting reproductive diapause. Experiments showed that the diapausing insects leave stores during the dry season. This factor subsequently induces a regression of population growth inside the stores at the end of the dry season. There was no development of the C. maculatus population in the present experiment, because of the low level of infestation in the field before harvest and the fact that climatic conditions were probably unfavourable for this species in the Niamey area. In stores, the rate of B. atrolineatus population increase is very high in a limited number of generations resulting in significant losses of cowpea seeds.