Barry Denholm

I. INTRODUCTION The cryptonephridial or rectal complex (CNC) is an organ architecture occurring in many insects that incorporates parts of the digestive and renal organs. It is remarkably prevalent and occurs in some of the largest and most evolutionarily successful insect groups including within Coleoptera and Lepidoptera (Fig. 1A–C), indicating its functional importance. The renal or Malpighian tubules (MpTs) are blind-ending tubes opening into the gut, into which they expel fluid.

Abstract Rectal or cryptonephridial complexes have evolved repeatedly in arthropods, including in beetles where they occur in ~190,000 species of Cucujiformia and Bostrichoidea, and Lepidoptera where they occur in ~160,000 species. Sections of the Malpighian/renal tubules coat the outer surface of the rectum, acting as powerful recycling systems of the gut contents, recovering water and specific solutes.