Tetrabothrus borneensis CAMERON, 1943

Assing, Volker, 2016, On some Lomechusini of the Palaearctic and Oriental regions (Coleoptera: Staphylinidae: Aleocharinae), Beiträge Zur Entomologie = Contributions to Entomology 66 (1), pp. 13-111 : 101-102

Tetrabothrus borneensis CAMERON, 1943

( Figs 160–162 , 444–449 )

Tetrabothrus borneensis CAMERON, 1943: 140 .

Type material examined: Holotype ♀: “ Mt Poi , 5000' / TeT. borneensis Cam. Type / M. Cameron. Bequest. 1955- 147 / Holotype / Holotype Tetrabothrus borneensis Cam. , det. R.G. Booth 2015” ( BMNH).

Additional material examined: Malaysia: 1 ♂ [teneral], Borneo, Sabah, Sandakan , S Lokan, flight interception trap, III.1997, leg. Chung ( BMNH) ; 9 exs., Sabah, Sandakan, Sepilok , X.1996, leg. Chung ( BMNH, cAss) ; 2 exs., same data, but III.1997 ( BMNH) . Indonesia: 9 exs., Borneo, Kalimantan Tengah, confluence of Busang and Rekut , 0°03'S, 113°59'E, flight interception trap, VIII.2001, leg. Brendell & Mendel ( BMNH, cAss) .

Comment: The original description is based on a unique type specimen from “Mt. Poi [= Mount Pueh; 1°48'N, 109°41'E], altitude 5,000 ft. ” ( CAMERON 1943). A dissection of the holotype revealed that it is a female. Remarkably, when distinguishing Tetrabothrus femoralis from T. borneensis, PACE (2014) states that the “aedeagus of this new species is more similar to that of T. indicus CAMERON, 1939 from Bengal, than to that of T. borneensis CAMERON, 1943 from Borneo, of which I have seen specimens of the type series”, although there appears to be only a single (undissected) female type specimen.

Redescription: Species of variable size; body length 4.3–5.8 mm; length of forebody 1.8–2.4 mm. Coloration variable: body reddish to blackish-brown; elytra usually at least indistinctly bicoloured with the anterior portion paler than the posterior portion; legs pale-reddish to brown; antennae blackish-brown with reddish antennomeres I–III.

Head ( Fig. 160 ) strongly transverse, distinctly narrowed behind eyes, extensively impunctate in the middle; punctation in lateral dorsal portions very fine and sparse. Eyes large and bulging, approximately three times as long as postocular region in dorsal view, or nearly so. Antenna ( Fig. 161 ) 1.0– 1.3 mm long.

Pronotum ( Fig. 160 ) of somewhat variable shape, 1.12– 1.17 times as broad as long and 1.05–1.17 times as broad as head, strongly convex in cross-section; punctation very fine and of variable density.

Elytra ( Fig. 160 ) approximately 0.9 times as long as pronotum; punctation very fine and rather dense; pubescence long and suberect. Hind wings fully developed. Metatarsomere approximately as long as the combined length of metatarsomeres II and III.

Abdomen ( Fig. 162 ) narrower than elytra and with moderately deep anterior impressions on tergites III–VI; tergite III with two, tergites IV–VI with four setiferous punctures at posterior margin; tergite VII without nonsetiferous punctation and with pronounced palisade fringe at posterior margin; tergite VIII with numerous setae at and near posterior margin; posterior margin of tergite VII with palisade fringe; posterior margin of tergite VIII truncate.

♂: posterior margin of sternite VIII nearly truncate in the middle ( Fig. 449 ); median lobe of aedeagus ( Figs 444–448 ) of variable size, 0.43–0.55 mm long; ventral process rather short, its shape not very distinctive and somewhat variable; paramere longer than median lobe, its apical lobe of moderate length.

Intraspecific variation: This species is subject to pronounced intraspecific variation of size, coloration, shape of pronotum, size of the median lobe of the aedeagus, and the shape of the ventral process of the aedeagus. In the material from Sabah, the size of the median lobe of the aedeagus ranges from 0.48 to 0.55 mm and the apex of the ventral process tends to be longer and more slender in lateral view, whereas in the males from Kalimantan Tengah the length of the median lobe ranges from 0.43 to 0.47 mm and the apex of the ventral process tends to be shorter. The holotype differs from the examined nontype material by paler coloration, sparse punctation of the pronotum, and slightly greater body size.

Comparative notes: Tetrabothrus borneensis is not very distinctive regarding its external characters and characterized particularly by the shape of median lobe of the aedeagus. The aedeagus somewhat resembles that of T. puetzi ( China, Taiwan), from which T. borneensis is readily distinguished by much paler legs with undilated femora alone.

Distribution and natural history: The examined material was collected in four localities in Borneo, one in Sarawak (type locality), two in Sabah ( Malaysia), and one in Kalimantan Tengah ( Indonesia). The species was doubtfully recorded from the Danum Valley (Sabah) based on three females by PACE (2014). The examined non-type material was collected with flight interception traps. One specimen collected in March is teneral.

Figures

Figs 160–180. Tetrabothrus borneensis, holotype (160–162), T. punctiventris (163–166), T. sulawesicus (167–169), Zyras illecebrosus, paratype (170–172), Z. gibbus, holotype (173–177), and Z. quasar, holotype (178–180): forebody (160, 163, 167, 170, 173, 178); antenna (161, 164, 168, 171, 174, 179); abdomen (162, 165, 169, 172, 175, 180); tergite VIII (166); tergite III (176); tergites VII– VIII (177). Scale bars: 160–165, 167–175, 178–180: 1.0 mm; 166, 176–177: 0.5 mm.

Figs 442–458. Tetrabothrus collucatus (442–443), T. borneensis (444–449), T. punctiventris (450–451), T. sulawesicus (452–454), Zyras illecebrosus, paratype (455–456), and Z. quasar, holotype (457–458): median lobe of aedeagus in lateral and in ventral view (442–445, 450–453, 455–458); apico-ventral portion of median lobe in lateral view (446–448); male sternite VIII (449, 454). Scale bars: 0.2 mm.