EFFECTS OF JUVENILE-HORMONE AND JUVENILE-HORMONE ANALOGS ON THE PHASE-BEHAVIOR OF SCHISTOCERCA-GREGARIA AND LOCUSTA-MIGRATORIA

Phase behaviour of Locusta migratoria and Schistocerca gregaria has be en studied using animals kept isolated (representing the solitary phas e) and reared under crowded conditions (representing the gregarious ph ase). Social aggregation (grouping), marching activity and aggression/ flight behaviour (reactions to confrontation) were monitored separatel y in adults and/or hoppers of different larval stages. All three quali ties of behaviour revealed characteristic and highly significant diffe rences between isolated and crowded locusts. Effects of JH III and thr ee JH analogues on the phase behaviour of crowded locusts have been an alysed. Aggregation was significantly reduced by all compounds in a do se-dependent manner suggesting a ''solitarization'' effect and a rathe r direct implication of endogenous JH in this behavioural parameter. J H analogues had, surprisingly, a stimulating effect on the marching ac tivity of crowded locusts. This might be caused by pharmacological sid e-effects of the JH analogues. Crowded locusts showed almost exclusive ly ''weak'' reactions to confrontation with decoy animals. After treat ment with JH analogues, the test animals exerted more ''strong'' and l ess ''weak'' reactions, thus indicating a tendency towards ''solitariz ation''. Generally, L. migratoria was slightly less responsive than S. gregaria to the tested compounds. JH III was less effective than the JH analogues. The varying strength of impact which the compounds had u pon the three behavioural qualities could reflect a differential invol vement of endogenous JH in these parameters.