Evidence for the independent evolution of a rectal complex within the beetle superfamily Scarabaeoidea.

Rectal or cryptonephridial complexes have evolved repeatedly in arthropods, including in beetles where they occur in ∼190,000 species of Cucujiformia + 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. There are hints that a rectal complex evolved independently within another beetle group, Scarabaeoidea.