Atheta (Microdota) biformis, Assing, 2021

Assing, Volker, 2021, New species, synonymies, combinations, and records of micropterous Athetini from China (Coleoptera: Staphylinidae: Aleocharinae), Beiträge Zur Entomologie = Contributions to Entomology 71 (1), pp. 87-101 : 100

Atheta (Microdota) biformis spec. nov.

urn:lsid:zoobank.org:act:30A8940E-5B8A-4E27-997F-777E8FFF3E80

(Figs 11–14, 52–60)

Type material: Holotype : “P. R. CHINA, Yunnan, E slope Cangshan at Dali, N 25°40'14.7" E 100°06'12.0", 17.v.2010, 3827 m, sifting16, V. Grebennikov / Holotypus  Atheta biformis sp. n., det. V . Assing 2020 ” ( CAS). Paratypes: 7 , 26 : same data as holotype ( CNC, cAss); 9 , 21: “P. R. CHINA, Yunnan, E slope Cangshan at Dali , N 25°39'54.7" E 100°06'04.5", 19.v.2010, 3815 m, sifting19, V . Grebennikov ” ( CNC, cAss); 2 , 6 : “P. R . CHINA, Yunnan, E slope Cangshan at Dali, N 25°40.07.6" E100°06'12.9", 19.v.2010, 3887 m, sifting18, V . Grebennikov ” ( CNC, cAss); 3 , 15 : “P. R. CHINA, Yunnan, E slope Cangshan at Dali, N 25°39'54.4" E 100°05'53.0", 15.v.2010, 3991 m, sifting14, V . Grebennikov ” ( CNC, cAss); 2 , 13 : “P. R. CHINA, Yunnan, E slope Cangshan at Dali, N 25°40'24.1" E 100°05'57.6", 17.v.2010, 3806 m, sifting15, V . Grebennikov ” ( CNC, cAss); 8 , 12 : “P. R. CHINA, Yunnan, E slope Cangshan at Dali, N 25°40'01.9" E 100°05'45.5", 15.v.2010, 4063 m, sifting13, V . Grebennikov ” ( CNC, cAss): 2 : “ CHINA, Yunnan, Cang Shan at Dali, N 25°40'12" E 100°06'10", 3740 m, 05.vii.2011, 4063 m, sift37, V . Grebennikov ” ( CNC) .

Etymology: The specific epithet (Latin, adjective) alludes to the pronounced sexual dimorphism of the pronotum.

Description: Body length 2.3–3.3 mm; length of forebody 1.0– 1.2 mm. Habitus as in Fig. 11. Colouration: head reddish to blackish; pronotum reddish to dark-brown; elytra dark-yellow to brown; abdomen brown to blackish with the apex (segments VIII–X and posterior portion of VII) usually yellowish to reddish and often also the anterior segments somewhat paler; legs yellow; antennae brown with the basal three antennomeres yellowish.

Head (Figs 12–13) distinctly transverse; punctation moderately sparse, subject to sexual dimorphism; interstices with microreticulation. Eyes flat and rather small, composed of approximately 15 ommatidia. Antennae weakly incrassate; antennomeres IV weakly transverse, V–X of increasing width and increasingly transverse, X barely 1.5 times as broad as long.

Pronotum (Figs 12–13) 1.20–1.25 times as broad as long and 1.1–1.2 times as broad as head; punctation subject to pronounced sexual dimorphism; interstices with pronounced microreticulation.

Elytra (Figs 12–13) 0.60–0.65 times as long as pronotum; punctation dense and asperate, partly granulose; interstices with microsculpture. Hind wings completely reduced.

Abdomen (Fig. 14) broader than elytra; punctation fine, but distinct, moderately dense on anterior tergites and sparser on tergite VI; punctation of tergite VII and VIII subject to sexual dimorphism; interstices with microreticulation composed of predominantly transverse meshes; posterior margin of tergite VII with or without indistinct rudiment of a palisade fringe; tergite VIII subject to sexual dimorphism.

: head (Fig. 12) flattened or impressed dorsally and with sparse and distinct punctation; pronotum (Fig. 12) with conspicuously dense and coarse punctation and with pronounced microsculpture rendering the disc nearly matt; tergite VII (Fig. 14) with granulose punctation in posterior portion; tergite VIII (Figs 14, 55) with dense and coarsely granulose punctation in posterior half, posterior margin truncate; sternite VIII ( Fig. 56 ) nearly as long as broad, posterior margin strongly convex; median lobe of aedeagus usually 0.38–0.40 mm long (see notes on intraspecific variation) and shaped as in Figs 52–54 .

: head (Fig. 13) not flattened dorsally, with very fine punctation barely noticeable in the microsculpture; pronotum (Fig. 13) with very fine punctation and with moderately pronounced microsculpture, with subdued shine; tergite VII with fine and sparse punctation; tergite VIII ( Fig. 57 ) with very fine punctation, posterior margin broadly convex; posterior margin of sternite VIII weakly concave and with fringe of long and moderately modified marginal setae ( Fig. 58 ); spermatheca shaped as in Figs 59–60 .

Intraspecific variation: One of the dissected males has an aedeagus of significantly smaller size (0.33 mm) ( Fig. 54 ). This phenomenon (occasional occurrence of significantly smaller aedeagi) has been observed also in Schistoglossa curtipennis (SHARP, 1869) (J. Vogel, pers. comm.).

Comparative notes: Atheta biformis shares the conspicuous sexual dimorphism of the punctation of the head, pronotum, and apical tergites only with A. dimorpha (Baima Shan, Meili Xue Shan) , evidently a synapomorphy suggesting that both species represent adelphotaxa. The new species is distinguished from A. dimorpha by larger body size, a broader habitus (head and pronotum more transverse), coarsely granulose punctation on the male tergites VII and VIII (less distinctly granulose in A. dimorpha ), the shapes of the male tergite VIII and sternite VIII, a larger aedeagus ( A. dimorpha : median lobe approximately 0.3 mm long) of different shape, and by the shape of the spermatheca. For illustrations of A. dimorpha see ASSING (2006).

Distribution and natural history: The species was collected in rather larger numbers in Diancang Shan, North Yunnan, at high elevations (3740–4060 m). The sex ratio is strongly biased: only 25 % of the specimens are males.

Figures

Figs 47–60: Atheta qinlingica (47–51) and A. biformis (52–60). 47–48, 52–54 – median lobe of aedeagus in lateral and in ventral view (54: nanistic morph); 49, 56 – male sternite VIII; 50 – female sternite VIII; 51, 59–60 – spermatheca; 55 – male tergite VIII; 57 – female tergite VIII; 58 – posterior portion of female sternite VIII. Scale bars: 49–50, 55–58: 0.2 mm; 47–48, 51–54, 59–60: 0.1 mm.