Gnathoncus Jacquelin du Val, 1857

Lackner, Tomas & Leschen, Richard A. B., 2017, A monograph of the Australopacific Saprininae (Coleoptera, Histeridae), ZooKeys 689, pp. 1-263 : 16-18

Gnathoncus Jacquelin du Val, 1857 Figs 68, 69-80, 81-89, 90, 91-98, 99-102, 103-110, 754

Gnathoncus Jacquelin du Val, 1857: 112. Type species Hister rotundatus Kugelann, 1792, designated by Thomson (1859: 75).

Diagnosis.

Cuticle brown to black, never metallic; frontal, supraorbital striae absent; pronotal hypomeron glabrous; pronotal depressions absent; elytra occasionally imbricate, punctures on apical part of elytra sometimes forming longitudinal rugae; marginal epipleural stria double; fourth dorsal elytral stria never connected with sutural stria; apical elytral stria usually shortened; elytra with characteristic hooked appendix between fourth dorsal and sutural striae at elytral base; anterior ends of fourth dorsal elytral and sutural elytral striae form a small hook. Prosternum without prosternal foveae; median fossa often present; carinal prosternal striae strongly convergent anteriorly, united under sharp angle; lateral prosternal striae shortened, strongly convergent anteriorly; prosternal process flattened, broad; outer-lateral costa reaches prosternal process, its basal margin distinctly elevated; metaventrite of males at times longitudinally concave; ninth tergite of male genitalia divided longitudinally.

Biology.

Gnathoncus is predominantly composed of inquilinous species, present in the nests of birds or mammals; some species are found exclusively inside these nests where they are predators ( Kryzhanovskij and Reichardt 1976), presum ably preying upon larvae of fleas and other tiny arthropods. Some species, however, are occasionally collected on carrion. Both species of Gnathoncus occurring in the Australopacific Region are typical synanthropes and are often collected in pigsties, dovecotes or chicken coops.

Distribution.

Twenty-four species and subspecies are known to occur worldwide, most in the Holarctic Region ( Mazur 2011); several species were possibly distributed over the globe by human activity. In Australopacific Region two introduced species have been collected in New Zealand and Australia (Fig. 754).

Remarks.

This genus can most easily be confused with the species of Tomogenius , endemic to the Australopacific Region, by the combination of absent frontal and supraorbital striae (Fig. 69) and presence of two marginal epipleural striae. Species of the genus Gnathoncus differ from Tomogenius by having a smaller body size, but chiefly by the absence of two large median foveae on the apex of prosternal process (Fig. 702; present in Tomogenius ).

Key to the Australopacific species of the genus Gnathoncus Jacquelin du Val, 1857