Muscle activity underlying sexual behaviour in male locusts (Locusta migratoria) after normal and hormonally disturbed development

Abstract. . The activities of three sets of muscles, representing the major components of the abdominal muscle system, were recorded in the pregenital abdominal segments of adult males of Locusta migratoria. The muscular activities 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 dorsal versus ventral longitudinal muscles; the activity of the dorsoventral muscles is rather unpredictable, except in the sixth and seventh abdominal segments where they are regularly involved in hooking-up. Studies on male sexual behaviour-linked muscle activity in precocene-induced fifth-instar adultiforms and azadirachtin-induced fifth-instar over-aged nymphs revealed no distinct differences between these creatures and normal mature males. Therefore the muscle activities associated with 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 that morphogenesis and ethogenesis (i.e. formation of neural circuits controlling adult-specific behaviour) are not closely dependent on each other.