Aggressive Behavior in Olive Fruit Fly Females: Oviposition Site Guarding against Parasitic Wasps

Among Tephritidae flies, the females display agonistic behavior to maintain single oviposition sites and reduce larval competition for food. In the olive fruit fly, Bactrocera oleae, female-female aggressive interactions are characterized by reciprocal wing waving, chasing, head butting and boxing with forelegs. Little is known on tephritid aggressive behaviors directed towards natural enemies, with special reference to parasitoids attacking their young instars. In this study, we quantified the aggressive behavior of B. oleae females guarding their oviposition site against the braconid parasitoid Psyttalia concolor. The fly aggressive behavior displayed against the parasitoids was compared that directed towards paper dummies mimicking P. concolor adults. When a P. concolor female came close (<20 mm) to a B. oleae female guarding the oviposition site, the 91.67% of the flies displayed wing-waving, the 63.34% chased the parasitoid, the 45% showed head-butting, while boxing was observed only in the 26.67% of the aggressions. When paper dummies were tested, only the 66.67% of the flies displayed wing-waving, the 8.33% performed chasing, followed by head butting (5.00%) and boxing (3.33%). B. oleae displayed longer aggression bouts towards live wasps over dummies. Overall, this is the first evidence pointing out that tephritid aggressive acts, besides their role in intraspecific interactions, were also highly effective to displace parasitic wasps from the fly oviposition site. Further research on potential consequences on fitness traits arising from the above-discussed behaviors, as well as on parasitoid learning-mediated responses to tephritid aggressions, is urgently required.