Gnathoncus Jacquelin-Duval, 1858

Lackner, Tomáš, 2010, Review of the Palaearctic genera of Saprininae (Coleoptera: Histeridae), Acta Entomologica Musei Nationalis Pragae (suppl.) 50, pp. 1-254 : 116-117

Gnathoncus Jacquelin-Duval, 1858

Gnathoncus Jacquelin-Duval, 1858: 112 . Gnathoncus: THOMSON (1867) :391; SCHMIDT (1885a):283, 317; REITTER (1896):306; GANGLBAUER (1899): 378; REITTER (1904): 35; REITTER (1909): 290; JAKOBSON (1911): 641, 648; BICKHARDT (1916 –1917): 104; AUZAT (1917): 206; HORION (1935):238; REICHARDT (1941): 154, 157; MCGRATH & HATCH (1941):54; STOCKMANN (1957):67 –76; WEN- ZEL (1962):374, 380; HATCH (1962): 258; HALSTEAD (1963): 9, 11–13; HANSEN (1968): 295, 315; WITZGALL (1971): 166; MAZUR (1973): 27; KRYZHANOVSKIJ & REICHARDT (1976): 110, 113; MAZUR & KASZAB (1980): 6, 42; VIENNA (1980): 115, 117; MAZUR (1981a): 71, 87; MAZUR (1984):103; ÔHARA (1994): 215; DOWNIE & ARNETT (1996): 607, 612; MAZUR (1997): 213; BOUSQUET & LAPLANTE (1999): 141, 142; MAZUR (2001): 19, 30; KOVARIK & CATERINO (2001): 221, 224; YÉLAMOS (2002): 245, 246; MAZUR (2004): 92; BOUSQUET & LAPLANTE (2006): 79 –81.

Type species: Hister rotundatus Kugelann, 1792 , designated by C. THOM- SON (1859: 75).

Diagnosis. Cuticle brown to black, never metallic; frontal, supraorbital striae absent; pronotum flattened; pronotal hypomeron glabrous; pronotal foveae absent; punctures of pronotum often forming longitudinal rugae laterally (in Gnathoncus kiritshenkoi pronotal disc medially with curious tubercle); elytra often imbricate, punctures on apical part of elytra often forming longitudinal rugae; marginal epipleural stria usually double; fourth dorsal elytral stria never connected with sutural stria; apical elytral stria often shortened. In most species there is a 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 pre-apical foveae; median fossa often present; carinal prosternal striae strongly convergent anteriorly, often 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 often longitudinally concave; ninth tergite of male genitalia divided longitudinally.

Differential diagnosis. Gnathoncus is most similar to the presumably related genera Eremosaprinus and Myrmetes sharing with them several putative synapomorphies: absent frontal and supraorbital striae, body without metallic luster and longitudinally divided ninth tergite of male genitalia. Gnathoncus differs from Eremosaprinus chiefly by the presence of lateral prosternal striae (absent in Eremosaprinus ) and shorter meso- and metatibiae. From Myrmetes , it differs by the presence of sutural elytral stria (absent in Myrmetes ), punctate dorsal surface (impunctate, matt in Myrmetes ), outer margin of protibia with teeth (only short denticles present in Myrmetes ) and the characteristic hooked appendix between the fourth dorsal elytral and sutural elytral striae (absent in Myrmetes ). Superficially also similar the sole Palaearctic representative of the subgenus Neosaprinus of the genus Euspilotus , E. (Neosaprinus) perrisi , but the species of Gnathoncus differ from it by absent preapical foveae and flattened and broad prosternal process (distinctly convex in E. (Neosaprinus) perrisi ). Female specimens of E. (Neosaprinus) perrisi also possess curious pygidial sulci ( Figs. 162–167 ) that are always absent in Gnathoncus .

Biology. Predominantly inquilinous genus, its representatives are found within nests of birds or mammals; some species are found exclusively inside these nests where they are an active and important part of the local communities ( KRYZHANOVSKIJ & REICHARDT 1976: 114). They presumably prey upon larvae of fleas and other tiny arthropods thus reducing their number within the nests. Some species, however, are occasionally collected also on carrion. At least one species ( Gnathoncus cerberus Auzat, 1923 ) lives cavernicolously, probably feeding on flies and other arthropods developing in guano. Several species of Gnathoncus (e.g. Gnathoncus rotundatus ) are typical synanthropes and are often collected in pigsties, dovecotes or chicken coops.

Distribution. Twenty-four species and subspecies are known to occur world-wide ( MAZUR 1997); several species were possibly distributed over the globe by human activity. However, most of the species are found in the Holarctic Region.

Species examined. Gnathoncus baeckmanni Reichardt, 1941 , G. brevisternus Lewis, 1907 , G. buyssoni Auzat, 1917 , G. cerberus Auzat, 1923 , G. communis ( Marseul, 1862) , G. disjunctus disjunctus Solskij, 1876 , G. disjunctus suturifer Reitter, 1896 , G. kiritshenkoi Reichardt, 1930 , G. nannetensis ( Marseul, 1862) , G. nidorum Stockmann, 1957 , G. potanini Reitter, 1896 , G. pygmaeus Kryzhanovskij, 1976 , G. rotundatus ( Kugelann, 1792) , G. semimarginatus Bickhardt, 1920 , G. turkmenicus transcaucasianus Olexa, 1992 , G. turkmenicus turkmenicus Olexa, 1992 , G. wassiliefi Normand, 1935 , Gnathoncus spec. nov.

Discussion. This is most likely a monophyletic taxon, well delineated by the presence of at least two synapomorphies, e.g, short hooked appendix between the fourth dorsal elytral and sutural elytral striae and double marginal epipleural stria. The longitudinally divided tenth abdominal tergite of males can be accounted among synapomorphies shared also with taxa Eremosaprinus , and Myrmetes . As mentioned above, together with Eremosaprinus and Myrmetes , these three taxa constitute the most basal ‘grade’ of the Palaearctic Saprininae (see Diagnosis of Eremosaprinus for details).

Figures

Figs. 162–167.Euspilotus (Neosaprinus) perrisi (Marseul, 1872), variability of female pygidial sulci. Figs. 162–165 after OLEXA (1975).