Chaetarthria, Stephens, 1835

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 : 250-251

Chaetarthria sp.

( Figs 11 , 12 A–K)

Material examined. SAUDI ARABIA: 1 ♂ 4 spec. ( NMPC): Jizan, Wadi Atoud, 17.8°N 42.366°E, at light, 245 m, 8.ii.2016, lgt. J. Bezděk & D. Král.

Diagnosis. Body 1.7–2.0 mm long; head and labrum black; pronotum and elytra uniformly yellowish; legs reddish to yellowish; dorsal surface without microsculpture; setae on dorsal surface peg-like ( Figs 12 J–K); elytron without elytral striae except sharply impressed sutural stria; lateral portion of elytra with weakly developed lateral-most series of punctures not impressed into stria; posterior margin of abdominal ventrites 2–5 bearing stout acute setae; male protibiae arcuate on inner margin; sternite VIII with median basal projection; sternite IX with wide tongue-like median portion; aedeagus 0.7 mm long; phallobase tubular, c. 1.4× longer than parameres; paremeres wide basally, narrowing from c. midlength to the quadrate apex, only slightly wider basally than apically in lateral view, completely encompassing median lobe; median lobe very narrow, reaching c. the level of apical fouth of parameres, basally reaching deeply into phallobase; gonopore subapical.

Discussion. The morphology of the male genitalia and the surrounding sclerites correspond precisely to those of Group 3: American Chaetarthria defined above (compare Figs 12 A–C, F–I with Figs 2 N–S). External characters support this assignment: dorsal setae are simple and cut-off apically (compare Fig. 12 K with Fig. 2 d), elytra lack longitudinal striae except for sutural stria, and pronotum and elytra are yellowish in color. The specimens above seem to stand close to the Argentinian species C. argentina Miller, 1974 and C. hermani Miller, 1974 of the C. atra group defined by MILLER (1974). When compared with the genitalia drawings and descriptions provided by MILLER (1974) it seems that the specimens examined here represent an undescribed species. We are however leaving it undescribed, as it is likely introduced and a more detailed comparison with the American species would be necessary to diagnose the species properly.

The presence of the species which is clearly an element of Neotropical fauna in Saudi Arabia is very unexpected. The first author discussed the problem with both collectors (J. Bezděk and D. Král) and with the person who mounted the specimens for NMPC (P. Pacholátko), and all of them excluded any possibility of mislabeling or mixing the Saudi Arabian material with Neotropical samples at any stage of the processing. Another alternative would be an unintended introduction of this species with some imported cargo. That could be facilitated by the fact that the species comes to light and may have been attracted to the cargo by strong lights usual in the cargo depositories and harbors. The introduction scenario is however called into question by the fact that both C. argentina and C. hermani (i.e. the species most similar to the Arabian one) live in dry areas of western Argentina (provinces of Tucumán and La Rioja) which is far from any harbor. The locality in Saudi Arabia where the specimens were collected is also quite far from the coast (c. 30 km) as well as from the nearest trade harbor (c. 100 km north). Even the introduction would hence need to be confirmed by a repeated catch.

Figures

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.

Fig. 12. Chaetarthria sp. from Saudi Arabia. A–C – aedeagus (A – dorsal, B – lateral, C – ventral). D–E – habitus (D – dorsal, E – lateral). F – details of parameres and apical part of the median lobe in ventral view. G – male tergite VIII; H – male sternite VIII; I – male sternite IX; J–K – elytral setae, SEM micrographs (J – general view; K – detail).

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.