BEHAVIORAL PLASTICITY IN THE STINGING ACT OF FEMALE ECTOPARASITOIDS

The plasticity of the stinging behaviour of female Eupelmidae (Eupelmu s vuilleti Crawford, E. orientalis Crawford Hymenoptera: Eupelmidae) w as analysed through the interrelationships of a parasitic community li ving on larval stage of Callosobruchus maculatus Fabricius (Coleoptera : Bruchidae). In traditional African grainstores, Eupelmus females hav e at their disposal all the larval stages of their host, Their exploit ation is revealed by the sting observed on the host caused by the ovip ositor of parasitoid females. This stinging behaviour begins immediate ly on the adult female's emergence, and thereafter there is a daily in crease in the number of hosts stung. Stinging activity is linked to th e age of the available hosts, but not all of the hosts available are e xploited by the two species studied. This absence of total exploitatio n could indicate a threshold of activity in the stinging acts which co uld be in part linked to the secretion activity of the poison glands o f parasitoid female. In females of E. vuilleti and E. orientalis the s tinging act is usually associated with egg-laying. The relationship be tween stinging and egg-laying is stronger in more advanced larval stag es of the host. In the presence of parasitized hosts, females of E. or ientalis and E. vuilleti can exhibit hyperparasitism. The majority of larvae (i.e. primary parasitoid) that have been hyperparasitized have been stung and a large number of them are completely inactive. However , E. vuilleti females deposited their eggs in the available space of t he pupation chamber of the host. The neonatal larvae from these scatte red eggs could exploit any available host without the female having 'p repared the ground' at the time of egg-laying. In Eupelmidae, all this happens as if there were a complementary action between the females a nd the neonate which could, if necessary, reinforce and/or compensate for the deficiencies in the host exploitation by the female.