CUTICULAR SURFACE HYDROCARBONS OF DESERT LOCUST NYMPHS, SCHISTOCERCA-GREGARIA, AND THEIR EFFECT ON PHASE-BEHAVIOR

The quantity of cuticular hydrocarbons is higher in solitarious nymphs of the desert locust, Schistocerca gregaria, compared to gregarious n ymphs, but the total hydrocarbon fraction of solitarious nymphs does n ot significantly divert behavioral transition of isolated nymphs to th e gregarious phase, while gregarious hydrocarbon extracts do. This sug gests that qualitative differences in composition are responsible for the biological effect. The profile of cuticular hydrocarbon components is similar in the two phases, but some peak ratios differ. Crowding o f solitarious nymphs leads to rapid changes in the profile of the hydr ocarbon fraction, suggesting that specific hydrocarbons are produced a nd secreted as a consequence. Isolating previously crowded nymphs has an opposite effect. The composition of cuticular hydrocarbons from the migratory locust, Locusta migratoria, which differs considerably from that of S. gregaria, does not induce the gregarious behavioral phase in solitarious nymphs of the latter.