EVIDENCE FOR MEDIATION OF 2 RELEASER PHEROMONES IN THE AGGREGATION BEHAVIOR OF THE GREGARIOUS DESERT LOCUST, SCHISTOCERCA-GREGARIA (FORSKAL) (ORTHOPTERA, ACRIDIDAE)

The response of nymphal and adult gregarious phase desert locust, Schi stocerca gregaria, to a choice of two columns of air, one permeated wi th airborne volatiles emanating from nymphs or adults and the other un treated, was investigated in a single-chamber bioassay arena. The nymp hs, whether released individually or in groups, preferred to be within the precinct of the air column treated with airborne volatiles of the nymphs but were indifferent to volatiles of the adults. Conversely, o lder adults responded only to their own volatiles but not to those of the nymphs or young adults. The young adults were responsive only to v olatiles of the older adults. Charcoal-trapped volatiles from the nymp hs and the adults reproduced the effect of living locusts. These resul ts indicate that there are two different aggregation pheromones in S. gregaria: a juvenile pheromone produced by nymphs and an adult pheromo ne specific to adults.