Functional morphology of pylorus and rectal glands in Reduviidae (Insecta—Heteroptera)

Abstract

Anatomical and histological studies of the alimentary organs of sixteen reduviids, with diverse food habits indicate structural variations. The terminal part of the tubular second midgut of these predaceous insects has a permanent sac-like region with distinct histology, concerned with absorption of digested food. In addition, the digestive system is characterised by a reduced pylorus with pyloric-intestinal and pyloric-rectal valves, surrounded by flask-shaped ampullae of the four malpighian tubules. The ampullary cells with their filamentous apices and with fibrillar cytoplasmic processes are concerned with. water absorption. Commonly in all these terrestrial insects, the anterior end of the rectum also bears a well-developed, inverted cup-like rectal gland, the cells of which also absorb water from the excreta stored in the impermeable, intima lined rectum. Members of Ectrichodiinae show simple ampullary cells and a unique rectum, reported for the first time among reduviids with scattered dome-shaped glandular cells as found in Homoptera and in some phytophagous Heteroptera. The simple nature of the alimentary organs indicates its primitive organization within the reduviid subfamilies.