Bolitogyrus caesareus (Bernhauer, 1915)

Brunke, Adam J., 2017, A revision of the Oriental species of Bolitogyrus Chevrolat (Coleoptera, Staphylinidae, Staphylininae), ZooKeys 664, pp. 1-97 : 18-21

Bolitogyrus caesareus (Bernhauer, 1915) Figs 1C, 3A, 4C, 10 A–C, 19C (map)

Cyrtothorax caesareus Bernhaeur, 1915: 146.

Cyrtothorax borneensis Cameron, 1942: 138, syn. n.

Type locality.

Mt. Matang, Sarawak, Borneo, Malaysia.

Type material.

Cyrtothorax caesareus Bernhauer, 1915.

Holotype (♂, FMNH) [dermestid damage]. Borneo. Matang, 26.XII.1913, Moulton, Sarawak Museum [handwritten] / 18 [handwritten] / Cyrtothorax caesareus Brnh, Typus unic [handwritten] / Chicago NHMus, M. Bernhauer Collection [printed] / Holotype ♂, Cyrtothorax caesareus Bernhauer, 1915, det. A. Brunke 2017 [red printed label] / AJB0000396 [identifier label].

Type material.

Cyrtothorax borneensis Cameron, 1942, syn. n.

Type locality. Martapura, South Kalimantan, Borneo, Indonesia.

Holotype (♂, BMNH): Type [circle label with red border] / Martapura, S.E. Borneo, Doherty, 1891 [typed label] / C. borneensis TYPE Cam. [handwritten] / M. Cameron Bequest. B.M. 1955-147. [printed] / Holotype ♂, Cyrtothorax borneensis Cameron, 1942, det. A. Brunke 2017 [red printed label] / Bolitogyrus caesareus Bernhauer, det. A. Brunke 2017 [white printed label] / AJB0000398 [identifier label].

Cameron (1942) stated that his specimen was a female but it is actually a male with an aedeagus not appreciably different from that of the holotype of B. caesareus , and well within the range of variation seen by the present author for this taxon. Diagnostic characters given by Cameron included antennal and abdominal coloration but these are variable within B. caesareus and both extremes were observed at the same collection site (e.g., Danum valley).

Other material.

BRUNEI: Temburong: Kuala Belalong FSC, 260 m, 4.539 115.156, Dipterocarp forest, flight intercept trap, 8.II.1992, N. Mawdsley, 1 ♀, AJB0000481, (BMNH); same except II-III.1992, 1 ♀, AJB0000482 (BMNH).

MALAYSIA: Johor: Endau-Rompin National Park, Pulau Jasin, 50-400 m, 2.516 103.349, 19.III.1998, Dembicky & Pacholatko, 1 ♂, AJB0000480 (NHMB); Pahang: Gunung Benom, Lata Jarum (20 km NE Raub), 350-550 m, 19-22.II.1995, M. Strba & R. Hergovits, 1 ♀, AJB0000483 (NMW); Lata Lembik, 30 km NE Raub, 200-400 m, 22.IV-V.2002, E. Jendek & O. Sausa, 1 ♀, AJB0000486 (cSHI); Taman Negara, Tahan tr. [trail], 90-130 m, primary forest, 11.III.1993, Löbl & Calame, 1 ♂ 1♀, AJB0000397, AJB0000485 (MHNG). Sabah: Danum Valley, B.R.I., flight intercept trap, 14-16.II.2007, G. de Rougemont, 2 ♂, AJB0000473, AJB0000478 (cRou); Lahad Datu, Ulu Segama, Forest Reserve, Danum Valley F.C., 4°57.9'N 117°48.1'E, 200 m, 1° forest, flight intercept trap, 1.XI.2005, Mann, Slade and Villaneuva, 1 ♂ 3 ♀, AJB0000474, AJB0000475, AJB0000477, AJB0000479 (OUMNH); Ranau, Poring Hot Spring and Nature Reserve, 26.X.1990, G. de Rougemont, 1 ♀, AJB0000484 (cRou); Sandakan Division, Maliau Basin Conservation Area, trail to OG2, 287 m, old growth forest, flight intercept trap, 4.745 116.969, 1 ♀, AJB0000476, Mann (OUMNH).

Diagnosis.

Among the members of the Caesareus Group, the yellow-ringed black spot near the humerus of each elytron is unique to B. caesareus (Fig. 1C). At present, it cannot be confused with any other species of Bolitogyrus .

Redescription.

Measurements ♂ (n = 5): HW/HL 1.38-1.44; PW/PL 1.29-1.46; EW/ EL 1.15-1.28; ESut/PL 0.89-0.95; PW/HW 0.96-1.07; forebody length 5.5-6.0 mm.

Measurements ♀ (n = 5): HW/HL 1.36-1.41; PW/PL 1.25-1.36; EW/ EL 1.17-1.25; ESut/PL 0.93-0.96; PW/HW 0.97-1.02; forebody length 5.2-6.4 mm.

Coloration: body yellowish-red; head black except middle third of frons; elytra with distinct black spot margined with yellow, spot about one third the length of elytra; abdominal tergites III (entirely), IV (basally and medioapically), VI (entirely except very base), VII (entirely except for pale apical one fifth) and VIII (entirely) black; antennomere 1 yellowish except for occasionally darkened apex, 2 reddish with dark apical half, 3-7 dark brown, apical four or apical three (most common) pale yellow to almost white, apical segment asymmetrically dark on one specimen, a few specimens seen with an antennomere half dark and half pale yellow; palpi entirely yellow to dark orange, apices sometimes darkened.

Head distinctly transverse, dorsal surface with moderately dense but clearly separated, asetose punctures, frons nearly impunctate. Antennomeres 6-10 transverse and asymmetrical.

Pronotum variable in shape but always distinctly transverse, convex, pronotal margin greatly expanded to variable degree. Elytra weakly to moderately transverse depending on the degree of lateral dilation, slightly shorter than pronotum at middle, in addition to usual macrosetal rows on disc, scattered punctures bearing setae, nearly all punctures setose on epipleuron of elytron; elytral disc bearing yellow margin of humeral spot raised and impunctate.

Abdomen with disc of tergites III-V distinctly, VI narrowly or not impunctate at middle; sternites III-IV with basal line distinctly, V slightly projected posteriad at middle.

Median lobe in lateral view gradually narrowed toward distinctly to slightly hooked apex, slightly constricted at apical third, without median tooth (Fig. 10B); median lobe in parameral view with apical half spoon shaped, apex slightly acute and pointed (Fig. 10A); paramere slightly to very slightly shorter than median lobe, constricted in basal third, variably dilated at about midlength, peg setae distributed in marginal group, about 2-4 peg setae wide, sometimes forming a median group in basal half (Fig. 10C); apical margin of male sternite VII with very slight emargination, male sternite VIII with shallow but distinct emargination and broad triangular, flattened, glabrous area medially; male sternite IX distinctly expanded at midlength, with distinct emargination, disc mostly glabrous except for conspicuous, divergent pair of rows of long setae.

Female tergite X elongate triangular, constricted at about midlength, with elongate raised discal area that is strongly impressed longitudinally.

Distribution.

Figure 19C. Distributed on both Borneo and mainland Malaysia. No males were available from Brunei and these are only tentatively identified as this species.

Bionomics.

Bolitogyrus caesareus is an inhabitant of lowland, often primary, rainforest, up to an elevation of about 550 m. Specimens were collected February to April and September-October.

Comments.

No consistent differences could be found between specimens from mainland Asia and Borneo. Bernhauer (1915) speculated that this species might be termitophilous as it was sent to him along with many other specimens of species known to be termite guests. Similarly, one recent specimen was seen with a highly modified, likely inquiline, aleocharine rove beetle attached to its midleg. As in other staphylinines that are confirmed to be associated with termites (e.g., Taxiplagus ), the apical antennomeres of B. caesareus and its closest relatives are asymmetrical and slightly expanded, possibly to find social insects via airborne pheromones. While this species is unlikely to be a truly integrated ‘guest’ of termites, it is quite possibly a predator of wood-nesting termites and may become attracted to nests that have been physically compromised.