Arpedium ludgeri, Assing, 2007

ASSING, VOLKER, 2007, A new species of Arpedium from Kyrgyzstan (Coleoptera: Staphylinidae, Omaliinae), Zootaxa 1423 (1), pp. 63-66 : 63-65

Arpedium ludgeri sp. n.

(Figs. 1 –9)

Type material. Holotype ♂: " Kyrgyzstan, Issyk-Kul , Terskej-A[latau]., Torsor pass, 22.VII.2005, 41°56'48"N, 77°22'09"E, 3700–3850 m, l. L. Schmidt / Holotypus ♂ Arpedium ludgeri sp. n. det V. Assing 2006 (coll. Assing)" . Paratype ♂: same data as holotype (coll. Assing) .

Description. Measurements (mm) and ratios (holotype, paratype): total body length: 4.5, 5.0; length of antenna: 1.37, 1.48; head width (HW): 0.62, 0.68; width of pronotum (PW): 0.83, 0.86; length of pronotum (PL): 0.57, 0.62; length of elytra at suture from apex of scutellum to posterior margin (EL): 0.62, 0.76; combined width of elytra: 1.01, 1.09; length of metatibia (TiL): 0.69, 0.72; length of metatarsus without claws (TaL): 0.36, 0.39; PW/HW: 1.34, 1.27; PW/PL: 1.45, 1.39; EL/PL: 1.08, 1.22; TaL/TiL: 0.52, 0.54.

Habitus as in Fig. 1. Head with moderately fine puncturation, interstices on frons on average approximately as wide as diameter of punctures; pubescence moderately long, pale, and suberect; dorsal surface without distinct microsculpture; in front of ocelli with oblong and sharply delimited impressions. Eyes moderately small, distinctly projecting from lateral contours of head, slightly longer than postocular region in dorsal view. Maxillary palpus with apical palpomere 1.5–1.8 times as long as preapical palpomere. Antenna rather short; antennomeres IV–VI less than twice as long as wide; VII weakly oblong; VIII–IX approximately as wide as long; X weakly transverse (Fig. 4).

Pronotum distinctly transverse and wider than head (see measurements, ratios PW / PL and PW /HW, and Figs. 2–3), widest in anterior half; posterior angles obtuse, shortly rounded; posterior lateral area more or less distinctly depressed; puncturation variable, in holotype moderately pronounced, in paratype distinctly coarser and well-delimited, interstices on average as wide as or slightly narrower than diameter of punctures (Figs. 2–3); pubescence moderately long, pale, and suberect; microsculpture absent .

Elytra comparatively short, slightly longer than pronotum (see measurements and ratio EL/PL), and distinctly dilated caudad; puncturation distinct, but ill-defined; pubescence similar to that of pronotum; interstices without microsculpture. Hind wings reduced. Metatarsus approximately half the length of metatibia (see ratio TaL/TiL).

FIGURES 1–9. Arpedium ludgeri (3, 7, 9: holotype; 1–2, 4–6, 8: paratype): 1—habitus; 2–3—forebody; 4—antenna; 5—abdomen; 6–7—aedeagus; 8–9—apical portion of aedeagus. Scale bars: 1–3, 5: 1.0 mm; 4: 0.5 mm; 6–9: 0.1 mm.

Abdomen approximately 1.1 times as wide as elytra, widest at segments IV/V; puncturation moderately fine and conspicuously dense; pubescence more or less depressed, darker and shorter than that of forebody; all segments with pronounced microsculpture and almost matt; posterior margin of tergite VII with narrow rudiment of palisade fringe (Fig. 5).

Male: aedeagus as in Figs. 6–9, with semitransparent internal tube; parameres apically not distinctly dilated and with 2 setae (Figs. 8–9).

Etymology. The species is dedicated to the collector of the types, Ludger Schmidt (Hannover), in gratitude for the gift of his staphylinid by-catches from Kyrgyzstan.

Comments on generic assignment. Arpedium ludgeri combines characters typically observed in Arpedium with those of Eucnecosum , thus rendering the separation of these taxa on the generic level doubtful. Based on the absence of microsculpture of the forebody, the long apical palpomere of the maxillary palpus (similar to the condition in A. cribratum Fauvel ), the shape of the impressions in front of the ocelli, as well as the rather coarse puncturation of the head and pronotum, the new species would have to be placed in Arpedium , whereas in size, shape and length of the wings, the presence of distinct pubescence on the forebody, and the relatively short antennae it is more similar to species currently attributed to Eucnecosum . Moreover, a comparison of several species of Arpedium and Eucnecosum yielded no convincing evidence that both are distinct on the generic level. The characters indicated in the literature (see introduction) to distinguish the two taxa (e. g. presence/absence of microsculpture, length and density of pubescence, length of antennae, relative length of palpomeres) do not seem to justify such a distinction. Finally, I have been unable to appreciate the presence/absence of a subocular ridge as a useful character. This ridge is more or less pronounced in all Arpedium and Eucnecosum species , but can be seen in ventral aspect only in those species with rather large eyes; in species with eyes of reduced size it is usually covered by the (more or less bulging) subocular portion of the head and can be seen only in lateral aspect. In conclusion, there is little doubt that Eucnecosum will eventually have to be treated as a subgenus again or may even have to be synonymised with Arpedium . Such changes, however, should be based on a thorough phylogenetic study of these taxa, which is not within the scope of the present paper.

Comparative notes. The new species is distinguished from other Palaearctic species of Arpedium and Eucnecosum as follows:

From A. quadrum by much smaller size, darker coloration especially of pronotum and elytra, less glossy, as well as more densely and distinctly pubescent forebody, reduced hind wings, shorter tibiae and tarsi, the much shorter antennae with less slender antennomeres, stouter maxillary palpi with relatively longer apical palpomeres, much smaller eyes, a distinctly more transverse and posteriorly more distinctly narrowed pronotum, distinctly finer and less well-defined puncturation of pronotum and elytra, much shorter and posteriorly more strongly dilated elytra, coarser and denser puncturation of the abdomen, and by the apically not distinctly dilated parameres of the aedeagus;

From A. nepalicum [characters taken from description by Coiffait (1982)], whose male sexual characters are unknown, by distinctly larger size ( A. nepalicum : 2.5 mm), darker coloration ( A. nepalicum : whole body reddish yellow), more pronounced posterior angles of the pronotum (in A. nepalicum broadly rounded), reduced hind wings (in A. nepalicum almost reaching apex of abdomen), denser puncturation and the more pronounced microreticulation of the abdomen (in A. nepalicum with shallow transverse microsculpture and glossy);

From the species currently attributed to Eucnecosum by the absence of microsculpture on the head and pronotum, by the longer impressions in front of the ocelli, by the stouter maxillary palpus with a relatively longer apical palpomere, by the distinctly more transverse, less convex (cross-section), and posteriorly more distinctly narrowed pronotum, the coarser puncturation of the pronotum, and by the denser puncturation of the abdomen.

Distribution and bionomics. The type locality is situated in eastern Kyrgyzstan, to the south of the Issyk-kul lake. The specimens were found under stones in stony grassland at an altitude of 3700–3850 m.

VOLKER ASSING Gabelsbergerstr. 2, D-30163 Hannover, Germany. E-mail: [e-mail]