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An investigation of the roof of the genital chamber in female plant-bugs with special emphasis on the “dorsal sac” (Hemiptera: Heteroptera: Miridae)

Summary In Miridae, the roof (dorsal wall) of the female genital chamber (bursa copulatrix) is often neglected in taxonomic studies, rarely represented in its entirety and its importance is usually underestimated. It contains several organs that are relevant for taxonomy and phylogeny, namely the ringed glands (parieto-vaginal glands) encircled by the widely used sclerotized rings, the spermathecal gland (vermiform gland), and the lateral oviducts; it may also display various “dorsal sacs” or pouches and other poorly known structures. The comparison of 24 species belonging to seven mirid subfamilies, and various additional literature data, suggest that the general architecture of the roof and the topographic relations of its different organs may be used to ascertain relationships of higher taxa. Information is mainly provided on the “dorsal sac”, i.e. a very variable pouch-like structure usually medially located in the vicinity of the lateral oviducts and the spermathecal gland. The dorsal sac is derived from the roof of the genital chamber, i.e. is a differentiation of the vaginal wall, and cannot be derived from the common oviduct as claimed by several authors. Apparently, the common oviduct does not exist in Miridae. A dorsal sac, variously shaped, occurs within most subfamilies examined (Cylapinae, Orthotylinae, Phylinae, Bryocorinae, Deraeocorinae, Mirinae). Some representatives of the tribe Mirini and Stenodemini (Mirinae) exhibit two types of dorsal sac. The subfamily Isometopinae as well as some species in each of the other subfamilies examined seem to be devoid of dorsal sac. Apparently, dorsal sacs are adaptive pouches which receive and lodge some parts of the phallus during copulation. At species level, the dorsal sac is informative in providing diagnostic characters. At supraspecific levels (genus, tribe, subfamily) the dorsal sac must be examined jointly with other equally informative structures of the roof: architecture of the sclerotized rings; location of the spermathecal gland; location, length and aspect of the lateral oviducts; aspect and size of the infoldings of the lateral margins of the genital chamber (mainly in Phylinae and Orthotylinae); shape of the genital chamber in dorsal view; and the presence, aspect and size of the paired lateral apodemes of the genital chamber.