Comparative anatomy of the defensive glands, ovipositors and female genital tubes of tenebrionid beetles (Coleoptera)

Abstract With the ultimate objective of determining higher phylogenetic relationships, the cuticular portions of the defensive glands, ovipositors and female genital tubes of 247 species from 178 genera were studied after clearing in sodium hydroxide. On the basis of these studies, the following evolutionary hypotheses are put forward. The most primitive tenebrionids are the lagriine groups and their allies. Ancestral tenebrionids were without defensive glands and some modern groups still are. Defensive glands evolved 4 times independently, once between sterna 8 and 9, and 3 times between sterna 7 and 8. Only one of the 7 8 glands shows much diversification beyond the primitive state. Primitively, these glands are simple, eversible, conical pouches with the gland tissue scattered on the reservoir dorsum. Advanced glands show increased reservoir size, localization of gland tissue, contriction of exit ducts, and specializations of reservoir walls. Ancestral tenebrionids have a female tube consisting of a blind, primary bursa copulatrix with ventral entry of the common oviduct and dorsal entry of the single, slender spermathecal gland tube. This condition persists in the lagriines and their allies. A strong tendency to evolve a separate, non-glandular spermatheca has led to its evolution at least 4 times independently. These are (1) a multiple, short-tubular spermatheca derived from the bursa copulatrix; (2) a single, short- to long-tubular spermatheca from the same source; (3) a cannister-shaped spermatheca derived from the basal portion of the spermathecal gland; and (4) a saccate spermatheca derived from the apical portion of the spermathecal gland. These 4 configurations are strong characters defining major lines of tenebrionid evolution. The ancestral ovipositor was probably elongate and appendage-like, and this condition is still present in some lagriines and their allies. The primitive ovipositor contains 2 sets of sclerites. The proximal paraprocts are rather simple and cyclindrical. The distal coxites are divided ventrally into 4 lobes with the fourth lobe bearing the gonostyles terminally. The paraprocts are stiffened ventrally by a pair of longitudinal baculi, while the first lobe of the coxites (the valvifer) are stiffened by a pair of transverse baculi. Much of the evolutionary change has involved reductions of various structures, but reorientation of the baculi and elongation and shortening of paraprocts and coxites have been important in certain groups. There is a strong tendency for the gonostyles to move to a lateral or dorsolateral position, and this is often accompanied by a reduction of the fourth lobe of the coxites. On the basis of these and other characters, several major lines of tenebrionid evolution become apparent: (1) the lagriines and their allies, probably including the adeliines, pycnocerines and goniaderines; (2) the diaperines and their allies; (3) the coelometopines, cnodalonines, strongyliines, talanines and their allies; (4) the tenebrionines, opatrines, helopines, toxicines, amarygmines and their allies. Some groups, such as the bolitophagines, share features with more than a single lineage and are difficult to place. Phylogeny within the major lines is discussed in general terms, as is the importance of internal characters for higher classification of Tenebrionidae.