A rectal valve is known from Bostrichiformia (e.g. Dermestidae, Bostrichidae, Ptinidae), Cucujiformia (e.g. Chrysmeloidea, Cleridae, Curculionoidea, Endomychidae, Tenebrionidae) and Buprestidae, associated with the cryptonephridial system for water recovery from fecal matter. The valve is probably homologous in at least the Bostrichiformia and Cucujiformia although the form it takes may not be. It comprises a sclerotized band lying in the wall of the rectum where this meets the perinephric membrane. The valve is plesiomorphically a narrow crimped ring, probably acting as a sphincter to retain fecal matter for water extraction. Apomorphically it extends longitudinally along the rectum and supports the perinephric chamber; this state has probably arisen independently several times. Larval and adult morphology may be similar or different. Within the Curculionoidea different apomorphic forms suggest monophyly of groups within the Anthribidae and Dryophthoridae, and within the curculionid subfamilies Entiminae, Mesoptiliinae, Molytinae and Cossoninae + Scolytinae, although limited weight should be placed on a single character. No support is provided for a relationship between the Platypodinae and Scolytinae. The genera Cylindrotypetes Zimmerman 1942 and Edaphotrypetes Morimoto 1995 are transferred from Molytinae: Phoenicobatini to Cossoninae: Pentrarthini.