Morphology of male and female terminalia and taxonomic revision of the burrower bugs genus Canthophorus (Heteroptera: Cydnidae)

The Palaearctic burrower bug genus Canthophorus Mulsant & Rey, 1866 (Heteroptera: Cydnidae) is revised. New data on the morphology and distribution are given. Structures of the female internal ectodermal terminalia and the completely inflated aedeagi in all species of the genus are described and illustrated for the first time. An extended differential diagnosis as a comparison with representatives of all Palearctic genera of the tribe Sehirini is given for the genus. Based on characters of the external morphology and terminalia of both sexes, new taxa are described: C. dubius sanigarumn. ssp., C. melanopterus mariaen. ssp., C. impressus hajastanicusn. ssp., and C. wagneri hyrcanicusn. ssp.; C. hissaricus Asanova, 1964 is downgraded to a subspecies level and included in C. mixtus Asanova, 1964. C. melanopterus niger (Vidal, 1950) is placed in synonymy with C. melanopterus melanopterus (Herrich-Schaeffer, 1835). A wide variability of the terminalia, especially in females, was found in C. melanopterus melanopterus; in the latter, six forms are described differing in the shape and size of sclerites in posterior pouches of the gynatrial sac and distributed mainly in the Mediterranean region. A key allowing identification of the species not only by males, but also by females, was compiled for the first time. It is shown that C. aeneus (Walker, 1867) [= Sehirus fuscipennis Horvath, 1899] and C. maculipes (Mulsant & Rey, 1852) have very significant differences from other species of Canthophorus in the male and female terminalia, and at the same time share some characters with the genus Adomerus Mulsant & Rey, 1866, including unique characters shared with several species of this group; therefore, the mentioned two species are transferred to the genus Adomerus.