The Effect of Competition on Foraging Behavior of a Thelytokous Parasitoid, Lysiphlebus fabarum (Marshall) on Aphis fabae Scopoli

Competition is a phenomenon that influences the size, structure and stability of insect communities, particularly on solitary endoparasitoids species. Although, competition normally incurs costs, it might be adaptive for the surviving individual. To determine which factors affect the patch use strategy of foragers under competition, the effect of previous experience with hosts already-parasitized or conspecific females on proportional time allocation to various behaviors associated with aphid exploitation was studied. To test this, individual L. fabarum females onto bean leaf disks infested with A. fabae in the laboratory was released and made continuous observations. Females that encountered aphids previously parasitized by a conspecific female prior to testing spent two times longer in host patches (leaf disks with 15 second-third instar of A. fabae) than females encountering only healthy aphids, also scored higher levels of activity for all foraging behaviors, number of hosts parasitized and superparasitized. Because of the significant effect of treatment on patch residence time, the incidence or duration of various behaviors was expressed as a fraction of patch residence time and then re-analyzed. Data showed that only incidence of searching and probing behaviors was higher in treatment females than their control counterparts. In the second experiment, females that encountered (90-120 min.) a conspecific prior to foraging behaved no differently in patch residence time, incidence or duration of various behaviors, and the number of aphids parasitized within the patch, than females that did not, suggesting that females did not respond to conspecifics as potential competitors.