EFFECTS OF JUVENILE-HORMONE TREATMENT ON PHASE-CHANGES AND PHEROMONE PRODUCTION IN THE DESERT LOCUST, SCHISTOCERCA-GREGARIA (FORSKAL) (ORTHOPTERA, ACRIDIDAE)

The roles of juvenile hormone III (JH III) on phase changes and pherom one production were examined in laboratory-reared gregarious desert lo cust, Schistocerca gregaria (Forskal). The hormone was applied to 5th instar nymphs and newly emerged adult locusts. Generally, the 5th inst ar nymphs exhibited a higher sensitivity to hormone treatments than th e adults. Hormone applications inhibited pheromone production (as meas ured by the amounts of phenylacetonitrile released). In addition, JH I II had a significant effect on the external colouration and absorbance ratios of the haemolymph pigments. It is concluded that the effects o f exogenous JH III on gregarious locusts represent a shift towards the solitarious phase. (C) 1997 Elsevier Science Ltd. All rights reserved .