HISTOMORPHOLOGY OF THE LARVAL AND ADULT DIGESTIVE SYSTEMS OF ALPHITOBIUS-DIAPERINUS (COLEOPTERA, TENEBRIONIDAE)

The digestive tracts of Alphitobius diaperinus (Panzer) larvae and adu lts consist of straight tubes with attached maxillary glands and Malpi ghian tubules. The foregut includes the pharynx, maxillary glands and esophagus with no well-defined crop or proventriculus. The midgut is a simple sac-like structure with a loose network of circular and longit udinal muscles. The hindgut is divided into two distinct sections, the anterior small intestine and the posterior large intestine. In larvae , the intestine is sigmoid in shape, and in adults a loop is formed. B oth life stages have six Malpighian tubules in a cryptonephridial arra ngement. The tubules are equally spaced around the hindgut in larvae, and two tubules are attached ventrally and four dorsally in adults. In cross-section, the foregut and hindgut of both life stages have, from lumen to haemocoel, an intima (with backward projecting spines in the foregut), epithelial cells, longitudinal muscles and well-defined cir cular muscles. Longitudinal muscles were present in the adult hindgut, but they were not conspicuous. By contrast, in larvae they were arran ged into distinct bundles between the rectal pads. The midgut has, fro m lumen to haemocoel, a peritrophic membrane, epithelial cells with a striated border, circular muscles and longitudinal muscles. The muscle arrangement of the midgut is reversed from that of the foregut and hi ndgut. The similarity in digestive tract structure between the two lif e stages suggests that they share similar feeding habits as generalize d scavengers.