Thysanarthria siamensis Hebauer, 2001

Fikáček, Martin & Liu, Hsing-Che, 2019, A review of Thysanarthria with description of seven new species and comments on its relationship to Chaetarthria (Hydrophilidae: Chaetarthriini), Acta Entomologica Musei Nationalis Pragae 59 (1), pp. 229-252 : 247-248

Thysanarthria siamensis Hebauer, 2001

( Figs 1C , 9 F–J, 11 )

Thysanarthria siamensis Hebauer, 2001: 399 .

Type material examined. HOLOTYPE: ♂ ( NHMW), THAILAND: MAE HONG SON: ʻN-THAILAND 1993 / Mae Hong Son env. / Ban Huai Po 24-30.VI. / leg. Schneider’.

Additional material examined. 1 ♂, 5 spec. ( NHMW, NMPC): INDIA: UTTARKHAND: Gauri (str.), Pauri Garhwal, left tributary of River Alaknanda, ca. 2 km upstream from Thamdar, along road to Marud, ca. 8 km from Srinagar, 730 m, 11.xi.2006, lgt. M. A. Jäch; 1 ♂, 2 spec. ( NHMW):River Suhma, Dehradun district, right tributary of river Ganga, ca. 5 km S Raiwala, ca. 10 km N Haridwar, 340 m, 9.ix.2006, lgt. M. A. Jäch. NEPAL: 1 ♂, 3 spec. ( NHMW): Gorkha, 26.–31.v.1992, lgt. Ivo Jeniš. LAOS: VIENTIANE: 1 ♂, 2 spec. ( NHMB): Laos, Vientiane , Vang-Vieng , 300, 102.4486, 18.92306, 10.v.2001 – 6.vii.2001, J. Kolibáč. THAILAND: MAE HONG SON: 1 ♂, 2 spec. ( NHMW): Huai Sua Tao, 11–17.v.1992, lgt. Jan Strnad.

Redescription. Body length 1.7–2.0 mm (holotype 1.8 mm), maximum body width 1.0– 1.2 mm (holotype 1.0 mm). Head and labrum black; pronotum uniformly yellowish or brown centrally and gradually getting paler towards margins; elytra uniformly yellowish to pale brown, with slightly darkened striae; legs yellowish. Head without microsculpture on interstices; punctation sparse, each puncture bearing yellowish pointed seta. Eyes separated by 3.1× the width of one eye in dorsal view. Pronotum with sparse setiferous punctation similar to that on head; interstices without microsculpture. Elytra with 10 striae sharply impressed except anteromedially (near scutellar shield) where neither striae nor serial punctures are visible; intervals weakly convex at midlength and near apex; interval punctation sparse, setiferous; interstices without microsculpture. Aedeagus ( Figs 9 F–J) 0.7 mm long. Phallobase widened in apical half, widest shortly below bases of parameres (slightly wider than parameres combined); weakly arcuate in lateral view. Parameres short, narrowly elongate, constricted at midlength, widened into rounded lobes apically; widely triangular in lateral view. Median lobe narrow, shorter than parameres, sharply pointed, without membranous apex of paired subapical lobes; gonopore circular, situated subapically.

Differential diagnosis. Thysanarthria siamensis is very characteristic by a relatively large aedeagus with lanceolate parameres and sharply pointed median lobe and is hence hard to be confused with any other species of the genus.

Biology. Specimens from India: Uttarkhand were collected at the sides of small to large stony rivers, microhabitat is unknown (M. A. Jäch, pers. comm.).

Distribution. The species is widespread, ranging from western Himalaya to central Thailand and northern Laos.

Figures

Fig. 1. Habitus of the Thysanarthria species and related Old Word Chaetarthriini.A – Thysanarthria bengalensis Hebauer, 2001, holotype; B – T. persica sp. nov., paratype; C – T. siamensis Hebauer, 2001, holotype; D – T. hongsonensis Hebauer, 2001, holotype; E – European Chaetarthria: C. seminulum (Herbst, 1797); F – large Old World Chaetarthria: C. nigerrima (Blackburn, 1891).

Fig. 9. Male genitalia of Thysanarthria species, holotypes. A–E – T. saurahana sp. nov. (A–C – whole aedeagus in dorsal, lateral and ventral view; D–E – detail of median lobe and parameres in dorsal and ventral view). F–J – T. siamensis Hebauer, 2001 (F–H – whole aedeagus in dorsal, lateral and ventral view; I–J – details of parameres and median lobe in dorsal and ventral view).

Fig. 11. Distribution of Thysanarthria and American Chaetarthria in Asia (A–B) and Near East (C), and examples of habitats of Thysanarthria (D–F). Localities: D – India, Madhya Pradesh, Bhadhua Chora stream ca. 10 km E of Matkuli Jhir, habitat of T. ceylonensis Hebauer, 2001; E – Republic of South Africa, Western Cape, 8 km NEE of Stanford, habitat of T. atriceps (Régimber, 1903), collecting spot marked by an arrow; F–G – Taiwan, Wufeng distr., 4.3 km SEE of Chaoyang University of Technology, habitat of T. chui sp. nov. (G – detail of sandy shore with one alive beetle). Photo D by M. Jäch, photo E by M. Fikáček, F–G by H.-C. Liu.