AGGREGATION PHEROMONE SYSTEM OF NYMPHAL GREGARIOUS DESERT LOCUST, SCHISTOCERCA-GREGARIA (FORSKAL)

Hexanal, octanal, nonanal, decanal, hexanoic acid, octanoic acid, nona noic acid, and decanoic acid were identified in the volatile emissions from fifth instars of Schistocerca gregaria by coupled gas chromatogr aphy-electroantennography (GC-EAD) detection and coupled CC-mass spect rometry (MS). In laboratory assays, synthetic blends of the eight comp ounds, with acids and aldehydes tested separately, evoked strong aggre gation responses from fifth instars, similar to responses evoked by a crude volatile extract of the nymphs. A nymphal fecal volatile phenoli c blend of guaiacol and phenol, which we have previously shown to evok e an aggregative response from different stages of the insect, signifi cantly synergized the activity of the blend of eight compounds, sugges ting mutually augmentative roles for nymphal and fecal volatiles in ev oking aggregation. These results indicate that the aggregation behavio r of gregarious second to fifth instars is modulated by three sets of pheromonal compounds: aldehydes and acids emitted by the nymphs themse lves and phenols associated with their feces.