Cuticular hydrocarbons control behavioural phase transition in Schistocerca gregaria nymphs and elicit biochemical responses in antennae

Cuticular lipid extracts have been shown to induce gregarious phase- related behaviour in Schistocerca gregaria solitarious nymphs. Analysis of various fractions of the cuticular lipids reveals that the behavioural response is specific to the hydrocarbon fraction. On exposure to cuticular hydocarbons, antennal preparations from crowded S. gregaria nymphs and adults generate a rapid and transient increase in the concentration of inositol trisphosphate (IP₃), whereas the level of cAMP is not affected. Antennal preparations from locust nymphs are more responsive to the hydrocarbon fraction than are preparations from adults. IP₃ generation is dose-dependent and species-specific. The notion that the cuticular hydrocarbons may interact with membrane receptors of antennal sensory cells is supported by the observation that hydrocarbon-induced IP₃ formation is significantly impaired in the presence of GDP-βS, an inhibitor of trimeric G-protein function. These findings confirm the view that components of cuticular hydrocarbons function in locusts as contact pheromones, specifically inducing gregarious phase behaviour, and that they initially act via induction of IP₃.