Thysanarthria atriceps ( Régimbart, 1903 )

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 : 236-238

Thysanarthria atriceps ( Régimbart, 1903)

( Figs 2a , 3B,G,H , 4 A–J)

Hydrobius atriceps Régimbart, 1903: 33 .

Hydrobius atriceps: KNISCH (1924a: 169 , catalogue); ZAITZEV (1908: 373, catalogue).

Thysanarthria atriceps: ORCHYMONT (1926a: 195 , transfer to Thysanarthria ); ORCHYMONT (1926b: 242, transfer to Thysanarthria explained in more detail, comparison with T. championi ); BALFOUR--BROWNE (1952: 134, distribution); BALFOUR- BROWNE (1957: 21, distribution); HANSEN (1999: 105, catalogue); HEBAUER (2001: 394, redescription and update of distribution); HEBAUER (2005: 39, distribution); HEBAUER (2006: 24, catalogue).

Type material. Not examined.

Additional material examined. MALAWI: 2 ♀♀ ( NMPC): Nkhotakota env., 12.92716°S 34.2831°E, 2–3.i.2002, J. Bezděk lgt. REPUBLIC OF SOUTH AFRICA: WESTERN CAPE: 3 ♂♂, 2 unsexed specimens ( NMPC): 8 km NEE of Stanford, in gravel/sand and small isolated pools at the sandy stream and on/in sandy banks along the stream, 34°25.0′S 19°32.4′E, 4–5.xii.2015, Arriaga, Fikáček, Seidel & Vondráček lgt. ( RSA 49). ZIMBABWE: 1 ♂, 7 unsexed specimens ( NMPC): 20 km W Gwanda, 120 km SE Bulawayo, 6.xii.1999, F. Kantner lgt.

Redescription. Body length 1.4–2.0 mm, maximum body width 1.1–1.3 mm. Head and labrum black, pronotum and elytra uniformly yellowish; legs reddish to yellowish. Head with strongly granulate microsculpture on interstices; punctation sparse. Eyes separated by 2.7× the width of one eye in dorsal view. Pronotum with sparse setiferous punctation similar to that on head; interstices with strongly granulate 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 A–J) c. 0.5–0.6 mm long. Phallobase slightly widened at base of parameres, slightly narrower than bases of parameres combined, weakly constricted at c. midlength, slightly bent in lateral view. Paremere widely rounded basally, narrowing in apical third, apex rounded. Median lobe narrow, membranous apically, without subapical projections; apex reaching c. level of apex of parameres; gonopore transversely oval, situated in distal third.

Variability. The examined specimens from the Republic of South Africa and Zimbabwe differ slightly in the shape of the basal part of the parameres (compare Figs 4 A–E and 4F – J) but seem to be identical in all other aspects including the morphology of the median lobe. Examination of much larger material from Africa covering the known distribution would be needed to reveal whether these differences may be constant and correlated with geography; without such a study we consider the observed differences to be intraspecific variation for the moment.

Differential diagnosis. Thysanarthria atriceps seems to be the only species occurring in Africa and is hence easy to identify. In form of the median lobe and parameres it resembles only the Arabian T. brittoni from which it differs in relatively longer and narrower parameres and less constricted phallobase.

Biology. The species seems to be usually collected at light. Examined South African specimens were collected from wet sandy banks of a small lowland stream ( Fig. 11E ), the beetles were found when the sandy parts were flooded with water or pressed to get submerged, which caused the beetles to float on the water surface.

Distribution. Central and southern part of Africa and Madagascar (where the type locality is situated); on African continent so far recorded from Togo, the Ivory Coast, Angola, Rwanda, Burundi, Malawi, Zimbabwe, Mozambique, and the Republic of South Africa ( HEBAUER 2006).

Figures

Fig. 2. Morphological differences among Thysanarthria and principal groups of Chaetarthria. A–Z – male genitalia and surrounding sclerites; a–e – details of elytral pubescence. A – Chaetarthria similis Wollaston, 1864; B–G, c – Chaetarthria seminulum (Herbst, 1797); H–M, b – Thysanarthria championi (Knisch, 1924); N–S, d – Chaetarthria panda Orchymont, 1939; T–Z, e – Chaetarthria malickyi Hebauer, 1995; a – Thysanarthria atriceps (Régimbart, 1903). A–D, K–M, Q–S, X–Z – aedeagus in dorsal, lateral and ventral view; E, J, P, V – male sternite 9; F, H, N, T – male sternite 8; G, I, O, U – male tergite 8. Figures a–e are all to the same scale.

Fig. 3. Morphology of Thysanarthria. A – mentum and maxillary palps; B – meso- and metaventrite and meso- and metafemora; C – head and prothorax in ventral view; D – antenna; E – ultimate maxillary palpomere with basal peg-like setae; F – metatarsus; G – ventral view with gelatinous substrance on the base of abdomen; H – detail of abdomen with gelatinous substance in the cavity on ventrites 1–2. A, C–F – Thysanarthria championi (Knisch, 1924); B, G–H – T. atriceps (Régimbart, 1903).

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.