EFFECTS OF JH-III AND JH-ANALOGS ON PHASE-RELATED GROWTH, EGG MATURATION AND LIPID-METABOLISM IN SCHISTOCERCA-GREGARIA FEMALES

Adult growth, egg maturation, fat body development and the strength of the adipokinetic reaction triggered by flight have been determined in laboratory-bred gregarious and solitary female Schistocerca gregaria. The body weight in young, maturing solitary females was higher than i n gregarious ones. Egg maturation, i.e. vitellogenin synthesis, vitell ogenin incorporation into the terminal oocytes and oocyte growth, star ted earlier in solitary than in gregarious females. Fecundity was also higher in solitary females. However, the proportion of fat body conte nt and strength of the adipokinetic reaction were much higher in grega rious females, which is seen as a prerequisite for long-distance migra tory flights. JH III and JH analogues were applied to newly emerged gr egarious females. JH III and JH analogues induced egg maturation soon after application; in the case of fenoxycarb and BASE 228743 even much earlier than in control solitary females. The latter JH analogues als o increased fecundity. JH III and JH analogues inhibited fat body deve lopment and suppressed the adipokinetic reaction. Thus they may suppre ss migratory flights. A possible employment of JH analogues in alterna tive locust control is discussed. JH III and JH analogues had an effec t on the fatty acid composition of the haemolymph 1,2-diacylglycerols. The treatment increased the proportion of the polyunsaturated fatty a cids. The effects of JH III and JH analogues on gregarious locusts are interpreted as solitarization effects. The role of JH in phase-relate d lipid metabolism and egg maturation is discussed. Our results are co nsistent with the hypothesis proposed for migratory insects, that migr ation and the underlying physiological processes are facilitated by lo w and female reproduction by high JH titres.