Hymenopteran contests and agonistic behaviour

Abstract

Summary The insect order Hymenoptera is speciose, diverse and common. Many wasps, bees and ants are well known for their ability, and propensity, to engage in agonistic interactions via biting and stinging (chemical injection), and may also interact using chemical deposition and volatile chemical release. Such behaviours are often exhibited during acquisition and defence of resources contested either by conspecifics or by allospecific hymenopterans. Here we examine the types of contests engaged in by social and non-social hymenopterans and highlight links between these and further aspects of evolutionary and applied biology. We first consider factors influencing the outcomes of contests between pairs of females over resources for reproduction. Studies of female–female contests in bethylids and several non-aculeate species of parasitoid wasps, especially scelionids, pteromalids and eupelmids, have addressed fundamental causes of the outcomes of contest interactions and have further linked contest behaviour to strategies of patch exploitation, clutch size and parental care. Further, we review links between the study of contest behaviour in parasitoids and their use as agents of biological pest control, particularly in terms of how contest behaviour may constitute intra-guild predation and influence strategic decisions to deploy single or multiple species of natural enemies. We then consider contests between males for access to mates, especially those engaged in by fig wasps and other wasps. Male–male contests are placed in the context of the evolution of alternative male morphs, mating systems, sex ratios and social behaviours. Finally, we return to female–female contests, this time examining them in the more complex context of the social Hymenoptera, in which both between-individuals (intra-colony) and between-group (inter-colony) contests occur.