Thysanarthria bifida, Fikáček & Liu, 2019

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 : 238-240

Thysanarthria bifida sp. nov.

( Figs 6 A–E, 11 )

Type material. HOLOTYPE: 1 ♂ ( NHMW), THAILAND: MAE HONG SON: Mae Ping, at light, 6.i.–30.ix.1991, lgt. Malicky. PARATYPES: 6 specimens ( NHMW, NMPC): same data as the holotype. CHIANG MAI: 2 spec. ( NHMW): Chiang Mai, Zoo, at light, 18.–25.iv.1988, lgt. Chantaramongkol & Malicky. SONGKHLA: 3 spec. ( NHMW): ʻab Ton Nga Chang WF’ , 4.–5.v.1993.

Description. Body length 1.2–1.5 mm (holotype 1.3 mm), maximum body width 0.8–0.9 mm (holotype 0.9 mm). Head and labrum black, pronotum and elytra uniformly yellowish; legs reddish to yellowish. Head with weak mesh-like microsculpture on interstices; punctation sparse, each puncture bearing a seta. Eyes separated by 4.0× the width of one eye in dorsal view. Pronotum with sparse setiferous punctation similar to that on head; interstices smooth, without microsculpture. Elytra with 10 striae sharply impressed except anteromedially (near scutellar shield) where neither striae nor serial punctures are visible; intervals convex at midlength and near apex; interval punctation sparse, setiferous; interstices without microsculpture. Aedeagus 0.5 mm long. Phallobase weakly and gradually narrowing from base of parameres towards base, slightly widened basally, weakly arcuately bent in lateral view; c. 2× longer than parameres. Paremeres short, wide basally, gradually narrowing towards apex, lateral face nearly continuously arcuate, apex bluntly rounded. Median lobe wide at level of gonopore, indistinctly constricted basally of it, apex membranous, widely rounded; subapical part with two triangular membranous lobes; apex reaching c. level of apex of parameres; gonopore transversely oval, situated below bases of paired projections.

Differential diagnosis. Thysanarthria bifida is easy to regonize by the median lobe bearing a pair of subapical membranous projections combined with the short parameres arcuately narrowing into simply rounded apices. In these characters it closely resembles T. trifida sp. nov. from which it mainly differs in smaller body size (1.2–1.5 mm in T. bifida , 1.9–2.0 mm in T. trifida ), shorter and wider parameres (compare Figs 6 A–E to 6 F–J) and the membranous apex of the median lobe widely rounded (compared to the pointed one in T. trifida ).

Etymology. The species name refers to the subapical pair of projections on the median lobe which make the apex of the median lobe seemingly bifid when observed under the microscope. Adjective.

Biology. Most examined specimens were collected at light, no more data are available about the biology.

Distribution. The species is so far known from three localities, two of which are situated in northwestern Thailand (provinces Mae Hong Son and Chiang Mai) and the last in the southernmost Thailand close to the border with Malaysia (province Songkhla). This indicates that the species is likely quite widely distributed but overlooked and rarely collected.

Figures

Fig. 6. Male genitalia of Thysanarthria species, holotypes (A–I, K–O) and paratype (J). A–E – T.bifida 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. trifida sp. nov. (F–H – whole aedeagus of the holotype in dorsal, lateral and ventral view; I – details of parameres of the holotype; J – same of the paratype). K–O – T. ceylonensis Hebauer, 2001 (K–M – whole aedeagus in dorsal, lateral and ventral view; N–O – details of median lobe and parameres 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.