The aedeagus,its musculature,and ‘retournement’ in Aspidomorpha miliaris F. (Coleoptera,Phytophaga, Chrysomelidae)

Summary

The aedeagus and its musculature in Aspidomorpha miliaris have been described in detail. They have been found to be closely comparable to those in the Chrysomelid Galerucella birmanica, which has been studied earlier from this standpoint by one of the present authors. In A. miliaris, however, the spiculum has shortened, and consequently the protractors of the aedeagus have been brought close to the proximal retractors of the aedeagus to form a basal muscular bulb for the aedeagus. The muscular bulb seems to help in maintaining the fluid pressure necessary for eversion of the internal sac of the aedeagus during copulation over a long period without strain on the general abdominal musculature. Shortening of the spiculum on the other hand has taken away the function of retraction from the proximal retractors of the aedeagus. The aedeagus is retracted after copulation by repeatedly stroking the protruding aedeagus with the hind legs and by pressing it against the substratum. The aedeagus undergoes ‘retournement’ through 180° after the adult has ecloded from the pupal skin. The ‘retournement’ is due to degeneration of the left member of the pair of protractors of the spiculum, while the right member exerts a unilateral pull on the dorsal surface of the genital tube, bringing about turning of the genital tube, and then survives as an apparently median muscle. In a small percentage of cases the left protractor survives to become the functional and the apparently median protractor of the spiculum, while the right member of the pair degenerates, and the consequent ‘retournement’ of the aedeagus is anti-clockwise.