THE TIME-COURSE OF BEHAVIORAL PHASE-CHANGE IN NYMPHS OF THE DESERT LOCUST, SCHISTOCERCA-GREGARIA

The time-course of behavioural phase change was investigated in nymphs of Schistocerca gregaria, using logistic regression analysis of behav iour recorded in a standard assay. Gregarization occurred very rapidly . Solitary-reared nymphs became markedly gregarious in behaviour withi n 1-4h of being placed in a crowd. These insects re-solitarized equall y quickly if removed from the crowd. Crowd-reared locusts also solitar ized within 1-4h, but this effect was not complete. Results indicate t hat, while behavioural gregarization is maximal within a few hours of crowding, solitarization is a two-stage process, changing rapidly at f irst, then more slowly as a function of the period of previous crowdin g.