MUSCLE-ACTIVITY UNDERLYING SEXUAL-BEHAVIOR IN MALE LOCUSTS (LOCUSTA-MIGRATORIA) AFTER NORMAL AND HORMONALLY DISTURBED DEVELOPMENT

The activities of three sets of muscles, representing the major compon ents of the abdominal muscle system, were recorded in the pregenital a bdominal segments of adult males of Locusta migratoria. The muscular a ctivities were associated with three consecutive actions of the male's mating behaviour: abdominal lowering, S-bending and hooking-up. These three actions depend mainly on the relative coordination of the dorsa l versus ventral longitudinal muscles; the activity of the dorsoventra l muscles is rather unpredictable, except in the sixth and seventh abd ominal segments where they are regularly involved in hooking-up. Studi es on male sexual behaviour-linked muscle activity in precocene-induce d fifth-instar adultiforms and azadirachtin-induced fifth-instar over- aged nymphs revealed no distinct differences between these creatures a nd normal mature males. Therefore the muscle activities associated wit h these adult-specific behavioural acts can be released precociously, i.e. their occurrence is not dependent on a distinct series of instars . Moreover, the results obtained with over-aged nymphs demonstrate tha t morphogenesis and ethogenesis (i.e. formation of neural circuits con trolling adult-specific behaviour) are not closely dependent on each o ther.