Thysanarthria brittoni Balfour-Browne, 1951

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

Thysanarthria brittoni Balfour-Browne, 1951

( Figs 4 K–O, 11 )

Thysanarthria brittoni Balfour-Browne, 1951: 215 .

Thysanarthria brittoni: HEBAUER (1997: 267 , catalogue); HANSEN (1999: 105, catalogue).

Type material examined. HOLOTYPE: ♂ ( BMNH), ʻType // W ADEN PROT / Wadi at foot of / Jebel Harir / ca. 5,000 ft / 1,2. xi.1937 // B. M. Exp. to / S. W. Arabia / H. Scott & / E. B. Britton / B. M. 1938-246 // J. Balfour-Browne det. / Thysanarthria / brittoni Type!ʼ.

Redescription. Body length 1.6 mm, maximum body width 1.0 mm. Head and labrum black, pronotum and elytra uniformly yellowish; legs reddish to yellowish. Head with weak microsculpture on interstices; punctation sparse, each puncture bearing 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 with weak microsculpture. Elytra with 10 striae sharply impressed except anteromedially (near scutellar shield) where neither striae nor serial punctures are visible; interval punctation sparse, setiferous; interstices without distinct microsculpture. Aedeagus ( Figs 4 K–O) c. 0.5 mm long. Phallobase strongly widened at base of parameres, c. as wide as bases of parameres combined, strongly constricted at c. midlength, slightly bent in lateral view. Paremere widely rounded basally, slightly narrowing in apical third, apex rounded, apices divergent from each other. Median lobe narrow, membranous apically, without subapical projections; apex reaching c. level of apex of parameres; gonopore transversely oval, situated in distal third.

Variability. BALFOUR- BROWNE (1951) mentions that the dorsal microsculpture of the head and pronotum, which is very weakly developed in the holotype, is stronger in some of the paratypes which are hence externally undistinguishable from T. atriceps .

Differential diagnosis and discussion. Thysanarthria brittoni is very similar to T. atriceps in all characters including male genitalia, which only differ in the proportions of the parameres including their slightly diverging apices, and by the more strongly constricted phallobase (see under T. atriceps for details). The difference of the genitalia of T. brittoni from the examined specimens of T. atriceps is bigger than the observed intraspecific variability of T. atriceps , which is the reason why we consider T. brittoni a separate species at the moment.

Biology. Unknown.

Distribution. Only known from the type locality in western Yemen, Arabian Peninsula (BALFOUR- BROWNE 1951).

Figures

Fig. 4. Male genitalia of Thysanarthria species. A–E – T. atriceps (Régimbart, 1903) from Zambia: 20 km W of Gwanda, coll. NMPC (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. atriceps from Republic of South Africa: 8 km NEE of Stanford, coll. NMPC (F–H – whole aedeagus in dorsal, lateral and ventral view; I–J – detail of median lobe and parameres in dorsal and ventral view); K–O – T. brittoni Balfour-Browne, 1951, holotype (K–M – whole aedeagus in dorsal, lateral and ventral view; N–O – detail 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.