Structure, function, and possible evolutionary significance of the constrictions in the male reproductive system of Calpodes ethlius (Hesperiidae, Lepidoptera)

Distinct constrictions occur between and within the various parts of the male genital tract in Lepidoptera. These consist of an epithelium surrounded by a single inner circular and multiple outer longitudinal layers of muscles. The thicker muscles and the lack of a secretion serve to keep the lumina of the constrictions closed between matings. They are opened by the pressure of secretion being pushed down the tubular tract by muscular action. It is proposed that their development in Lepidoptera has made possible the evolution of accessory glands in series, rather than in parallel, in those situations in which separation of secretory products is required.