The appearance and histological structure of the cuticle of the desert locust, Schistocerca gregaria (Forskål)

Abstract

No essential structural differences are encountered between the tergites and intersegmental membranes into which the fully developed dorsal abdominal cuticle of Schistocerca is differentiated. An exocuticle and an endocuticle are the principal layers seen throughout the cuticle, but a variation in their relative thickness allows of considerable flexibility in the intersegmental membranes. Both layers are virtually colourless, but owing to their transparency many of the pigments located in the underlying epidermis are visible through them. Still closer resemblance between the tergite and intersegmental membrane regions is encountered in the newly moulted cuticle, in which no hard exocuticle is yet developed. In this stage, however, the epicuticle, which is not readily recognized histologically in the fully hardened cuticle, is clearly seen in sections. It is shown to consist of the four well-defined layers--cuticulin, paraffin, wax and cement--already recognized in the epicuticle of Periplaneta (Dennell & Malek 1955a). The structural differences between the cuticles of Schistocerca and of Periplaneta are considered. It is suggested, in conclusion, that the exocuticle of Schistocerca, in spite of being colourless, is more similar to the amber-coloured zone of the exocuticle of Periplaneta than to the underlying colourless zone.