SEX-DIFFERENTIATION STUDIES RELATING TO RELEASER AGGREGATION PHEROMONES OF THE DESERT LOCUST, SCHISTOCERCA-GREGARIA

Behavioural responses of nymphs and adults in the gregarious phase of the desert locust, Schistocerca gregaria (Forskal) (Orthoptera: Acridi dae) were investigated in a single-chamber bioassay system to a choice of two columns of air, one permeated with airborne volatiles emanatin g from either sex of nymphs or adults and the other untreated. There w as no sexual differentiation in the production of or response to nymph al volatiles. Young adults of either sex did not produce a stimulus wi th significant activity. Of the older adults, only the males produced the aggregation stimulus to which both sexes were equally responsive. Charcoal-trapped volatiles from the two sexes of nymphs and adults evo ked similar aggregation responses. Antennae of the older adults showed significantly higher EAG responses than those of fifth instar nymphs to all four volatile collections, of which volatiles from older adult males were the most stimulatory and evoked the highest EAG amplitudes.