Flight tunnel responses of Diachasmimorpha longicaudata (Ashmead) (Hymenoptera : Braconidae) to olfactory and visual stimuli

Cohorts of mass-reared, naive Diachasmimorpha longicaudata, parasitoids of tephritid fruit flies, were released in a laminar airflow wind tunnel to st udy their responses to visual and olfactory stimuli associated with their h ost habitat. Parasitoids were five times more likely to land on yellow plas tic spheres emitting the odor of ripe, guava fruit (Psidium guajava L.) tha n to spheres emitting clean air. The rate of landing was not modified by th e presence of green artificial leaves adjacent to the spheres in the tunnel or by the inclusion of green leaf volatiles emanating with the guava odors . However, hovering activity was twice as frequent around spheres adjacent to artificial leaves than around isolated spheres. Oviposition activity on spheres emitting guava odor Mitts not affected by the presence of artificia l leaves nor by green leaf volatiles. This suggests that inexperienced D. l ongicaudata may be instinctively attracted to foliage and to fruit odor but that landing (arrestment) and oviposition are influenced more by odor than by the appearance of fruit or foliage. D, longicaudata are not instinctive ly attracted to larvae of Bactrocera dorsalis in the absence of host-habita t stimuli. More wasp activity occurred around oviposition units containing larvae if the odor of ripe/overripe guava was present. Successful wasp repr oduction occurred only in units with guava odor.