Thinodromus chagosanus (Bernhauer, 1922)

Makranczy, György, 2014, Review of the Thinodromus circulus species group (Coleoptera: Staphylinidae: Oxytelinae), Acta Entomologica Musei Nationalis Pragae 54 (2), pp. 539-554 : 548-551

Thinodromus chagosanus (Bernhauer, 1922)

( Figs 2 , 13–14 , 23–26 )

Trogophloeus (Carpalimus) chagosanus Bernhauer, 1922b: 167 (original description), SCHEERPELTZ (1933): 1081 (catalogue).

Thinodromus chagosanus: HERMAN (1970) : 387 (catalogue), HERMAN (2001): 1765 (catalogue).

Type locality. Chagos Archipelago, Diego Garcia, approx. 7°18ƍS, 72°24ƍE.

Type material examined. LECTOTYPE (here designated): J, ‘Chagos.; Diego Garcia \ 9.VII.[19]05 \ chagosanus; Bernh.; Cotypus. Scot \ Chicago NHMus; M. Bernhauer; Collection \ Lectotypus; Trogophloeus ; chagosanus Bernhauer ; des. Makranczy, 2013 \ Thinodromus ; chagosanus (Bernhauer) ; det. Makranczy, 2013 ’ ( FMNH).

Other material examined. CHAGOS ARCHIPELAGO: Diego Garcia, Pointe Marianne, 12.IV.1971, leg. A.M. Hutson ( BMNH accession number 1971-346), at light (1 microscopic slide, HNHM). SEYCHELLES: Mahé Sud, Anse à la Mouche, 1.–15.VIII.1972, leg. P.L.G. Benoit & J.J. van Mol (Miss. zool. belge aux Séchelles) (2 JJ MRAC, 1 J HNHM).

Redescription. Measurements (in mm, n = 4): HW = 0.54 (0.51–0.55); TW = 0.48 (0.45– 0.49); PW = 0.53 (0.50–0.56); SW = 0.655 (0.62–0.68); AW = 0.735 (0.68–0.76); HL = 0.35 (0.34–0.35); EL = 0.21 (0.21–0.22); TL = 0.04 (0.03–0.04); PL = 0.41 (0.40–0.42); SL = 0.665 (0.65–0.68); SC = 0.62 (0.61–0.63); FB = 1.43 (1.40–1.46); BL = 2.65 (2.60–2.69). Lustre and colour. Fine punctation on foreparts and shallow microsculpture of body providing a greasy lustre. Head, pronotum and abdomen brownish black, elytra very dark brown, sometimes slightly reddish apical edge and outer posterior corners often a little darker, black. Legs medium brown, apices of femora and middle of tibiae darker, blackish. Mouthparts and antennae dark brown, latter with ¿rst segment often lighter. Shape and sculpture. Forebody as in Fig. 2 . Head transverse, eyes very large, occupying sides of head, temples marked but very small, length insigni¿cant compared to that of eye. Neck delineated only by different, alveolate microsculpture, but without transversal groove. Antennae slightly elongate, antennomeres 4 and 5 1.05–1.08× and 1.31–1.35× longer than broad, antennomere 9 1.00–1.04× longer than broad, antennomere 10 approximately as long as broad. Pronotum rather transverse, strongly obtuse-angled anterior corners super¿cially appear somewhat rounded but still marked. Posterior half of pronotal sides quite straight, even feebly concave; posterior corners obtuse-angled and rounded. Horseshoe-shaped impression slightly marked except posterior/median part where rather impressed; slight lateral depressions connected by it. Middle of disc bearing pair of shallow depressions. Slight (thin) marginal bead (mostly lateral) of pronotum observable only in sublateral view. Elytra combined imperceptably broader than long, gently dilated towards apex, with a pair of small, oval, slightly elongate impressions behind scutellum and extending posteriorly in longitudinal impressions, connecting to somewhat depressed centre of elytral disc. Posterior elytral margin (slightly oblique) with very thin bead and in outer 1/3 with small membranous lobe protruding. Apex of abdominal tergite VII with palisade fringe. Punctation and microsculpture. Head and pronotum punctation rather ¿ne, but deep and quite dense, mixed in with colliculate miscrosculpture; interspaces only a fraction of puncture diameters. Epistomal suture marked as a less punctate/sculptured area, with trace of transversal strigulate microsculpture. Punctation less deep and dense on ridges, e.g. outside/along roundish depressions at centre of pronotal disc. Microsculpture more rough and scabrous in depressions and near posterior pronotal corners, on pronotum generally stronger on sides than centre of disc. Elytra with slightly larger punctures, but also larger interspaces with less distinct microsculpture so appearing a little more lustrous.Abdomen with scattered, ¿ne but distinct punctures, slightly imbricate or coriaceous microsculpture with isodiametric cells and a rather greasy lustre. Pubescence. Body setation short, ¿ne, but rather dense, hair sizes vary more on abdomen, apices of segments with longer hairs. Primary and secondary sexual features. Male sternite VIII as in Fig. 25 , male sternite IX as in Fig. 23 , male tergite X as in Fig. 26 , aedeagus as in Fig. 24 .

Differential diagnosis. Thinodromus chagosanus appears to be the only species in this species group with small (barely marked) temples.

Distribution. Known from the Seychelles and the Chagos Archipelago, therefore likely to be widespread across tropical islands of the Old World.

Remarks. The plate-like armature in the hypopharynx illustrated in MAKRANCZY (2006: 60, Fig. 42) is erroneously captioned as T. chagosanus , while in fact it belongs to T. thoracicus Gildenkov, 2000 (full taxonomic treatment in MAKRANCZY 2009), the correct one for T. chagosanus is in Fig. 14 . It must be noted that the two are of the same general structure but of slightly different shape. It is also remarkable that T. thoracicus has rather similar habitus ( MAKRANCZY 2006: 88, Fig. 115) to that of T. arcitenens (treated below). Of numerous existing syntypes in depositories, the lectotype is a male with clear genital traits and chosen to ¿x the interpretation of this species.

Figures

Figs 1–4. Forebodies of Thinodromus species. 1 – T. circulus (Bernhauer, 1922); 2 – T. chagosanus (Bernhauer, 1922); 3 – T. palustris (Bernhauer, 1922); 4 – T. arcitenens (Fauvel, 1905).

Figs 5–14. 5–10 – Thinodromus circulus (Bernhauer, 1922) (5 – mesotarsus; 6 – male sternite VIII; 7 – male tergite IX; 8 – male sternite IX; 9 – male tergite X; 10 – spermatheca); 11–12 – T. velutinus (Sharp, 1887) (11 – tergite X; 12 – spermatheca); 13–14 – T. chagosanus (Bernhauer, 1922) (13 – mesotarsus; 14 – platelike armature in hypopharynx). Scale bar: 0.06 mm for 14; 0.07 mm for 5, 13; 0.1 mm for 10–12; 0.12 mm for 8–9; 0.14 mm for 6–7.

Figs 20–24. 20 – Thinodromus velutinus (Sharp, 1887), tergite VIII; 21–22 – T. circulus (Bernhauer, 1922): 21 – tergite VIII, 22 – aedeagus; 23–24 – T. chagosanus (Bernhauer, 1922): 23 – male sternite IX, 24 – aedeagus. Scale bar: 0.1 mm for 20–21; 0.15 mm for 22–24.

Figs 25–30. 25–26 – Thinodromus chagosanus (Bernhauer, 1922): 25 – male sternite VIII, 26 – male tergite X. 27–28 – T. palustris (Bernhauer, 1922): 27 – male sternite VIII, 28 – male tergite X. 29–30 – T. arcitenens (Fauvel, 1905): 29 – male sternite VIII, 30 – male tergite X. Scale bar: 0.07 mm for 30; 0.08 mm for 28–29; 0.1 mm for 26–27; 0.11 mm for 25.