Gnathoncus Jacquelin du Val, 1857

Lackner, Tomáš, 2020, A review of Gnathoncus of Southeast Asia (Coleoptera: Histeridae: Saprininae), Acta Entomologica Musei Nationalis Pragae 60 (1), pp. 397-409 : 398

Genus Gnathoncus Jacquelin du Val, 1857

Gnathoncus : MΑƵUR (2011): 175 (catalogue); VιΕΝΝΑ +| RΑττο (2013): 30 (description of a new species from Iran); LΑർΚΝΕR et al. (2015): 113 (catalogue); LΑർΚΝΕR +| LΕඌർΗΕΝ (2017): 28 (diagnosis and key to the Australopacific Gnathoncus ).

Note. Complete list of synonymies and literature references of this taxon are given in LΑർΚΝΕR (2010: 105) and the reader is referred to them there. For the sake of completeness we only list the references published after LΑർΚΝΕR (2010) above.

Diagnosis. Members of the genus Gnathoncus can be easily distinguished from all other SE Asian Saprininae by the following external and genitalic characters: body rather small (PEL= 1.70–3.20 mm), uniformly dark-brown to black, without metallic hue; frontoclypeal suture (frontal stria) absent; dorsum punctate; pronotal hypomeron asetose, pronotum only with marginal pronotal stria (shortened in case of G. semimarginatus ); elytra with complete striae I–IV; between base of elytral stria IV and sutural elytral stria (that can be interrupted or present only as a short basal fragment) present a characteristic short, hooked appendix; lateral prosternal striae very short, reaching approximately mid-length of carinal prosternal striae; outer lateral costa of prosternal process reaching prosternal keel. Ninth tergite of male terminalia longitudinally divided; VIII sternite and tergite not fused laterally. For a key to the Thai Saprininae see MΑƵUR +| ÔΗΑRΑ (2003); for a key to the Indonesian Saprininae see ÔΗΑRΑ +| HΑRιτιΝι (2008). As yet, there is no key to the SE Asian genera of Saprininae , mostly due to the existence of undescribed taxa from Thailand and Vietnam (T. Lackner, unpublished).

Biology. Gnathoncus brevisternus was collected inside caves; G. rotundatus is a synanthrope often collected in anthropogenic settings; G. nannetensis was collected on carrion and in bird nests; G. sechuanus sp. nov. was collected under a mushroom on a tree trunk in a mixed forest. The biology of two SE Asian endemics ( G. vietnamicus and G. semimarginatus ) is unknown.

Distribution. In SE Asia, Gnathoncus is present mainly in the north of the region: southern China (Guangdong, Gansu, Sichuan), Taiwan, Nepal, northern Thailand and Vietnam. One unidentified species is known from Java ( Indonesia). The exact distribution of G. semimarginatus is unknown (its holotype was either collected in northern India or southern China, see below).