Hydroscapha khasiorum, Ek, Martin Fiká Č & Šípková, Hana, 2009

Ek, Martin Fiká Č & Šípková, Hana, 2009, New Asian Hydroscapha, with comments on male-female association of co-occuring species (Coleoptera, Myxophaga, Hydroscaphidae), Zootaxa 2286, pp. 31-48 : 37-39

Hydroscapha khasiorum sp. n.

(Figs 3–11, 24–27)

Type material. HOLOTYPE: male ( NMPC): “ INDIA, Meghalaya State (6) / E Khasi Hills, 11 km SW Cherra- / punjee, Laitkynsew, 21.–24.iv. / 2008, 25°12'N 91°40'E, 460m / Fikáček, Podskalská, Šípek lgt. // wet rock with algae/blue algae / and fallen leaves at side of / waterfall on small river surround. / by tropical forest, ca. 200m / upstream from living brigde”. PARATYPES: 14 males, 8 females ( NMPC, BMNH, GHUA, KSEM, MHNG, NHMW): same locality data as the holotype; 10 males, 15 females ( NMPC, BMNH, KSEM, MHNG, NHMW): “ INDIA, Meghalaya State (10) / E Khasi Hills, 11km SW Cherra- / punjee, Laitkynsew, 21.–24.iv. / 2008, 25°13'N 91°39'E, 810m / Fikáček, Podskalská, Šípek lgt. // seepage: wet rocks algae / blue algae/moss ca. 1.5–2 km / via rd. from ‘Cherrapunjee Holid. / Resort’ in direct. Cherrapunjee, / exposed”; 8 males, 18 females ( NHMW, NMPC): “NE INDIA, MEGHALAYA / SW of CHERRAPUNJEE / 25°13'–14'N 91°40'E / 5.–24.v. 2005, 900 m / P. Pacholátko lgt.”

Description. Measurements: Total body length: 1.16–1.50 mm (median: 1.32 mm, n=15; not measured in holotype). Length of fore body: 0.84–0.97 mm (median: 0.90, n=47; holotype: 0.84 mm); males: 0.84–0.95 mm (median: 0.92 mm, n=20); females: 0.84–0.97 mm (median: 0.88 mm, n= 27). Elytral length: 0.52–0.65 mm (median: 0.57 mm, n=47; holotype: 0.60 mm); males: 0.55–0.65 mm (median: 0.60 mm, n=20); females: 0.52–0.62 mm (median: 0.57 mm, n=27). Maximum width of elytra combined: 0.53–0.63 mm (median: 0.58 mm, n=47; holotype: 0.60 mm); males: 0.55–0.63 mm (median: 0.60 mm, n=20); females: 0.53–0.62 mm (median: 0.57 mm, n=27).

Colouration: Body brown to dark brown; head, anterior and posterior margins of pronotum and elytral suture slightly darker.

Antenna: Antennomere II 1.7–2.1 times longer than wide; antennomere VIII slightly asymmetrical, 2.1– 2.6 times longer than wide (2.3–2.6 times in males, 2.1–2.3 times in females).

Male: Sternite V straight on posterior margin, with setae becoming denser towards posterior margin, densely arranged through entire width of sternite, not forming distinct tufts; posterior margin not denticulate. Sternite VI with regularly arranged setae in posterior 0.75, with weak tufts consisting of few setae only. Sternite VII with postero-median portion projecting into wide low obtuse lobe, posterior setae irregularly arranged in tufts along posterolateral margins. Aedeagus 0.29–0.33 mm long (median 0.31 mm, n=13, holotype: 0.32 mm), slightly sinuate in lateral view, continually narrowing apicad, apex slightly to distinctly bent ventrad.

Female: Sternite VI simply rounded posteriorly. Tergite VI projecting into narrow median lobe on posterior margin.

Differential diagnosis. The males are very similar to H. monticola Löbl, 1994 , from which they may be reliably distinguished only by the shape of the posterior margin of sternite V (straight in H. khasiorum , sinuate in H. monticola ) and by the different chaetotaxy of sternite V (long setae situated on the entire posterior margin in H. khasiorum , two tufts of densely arranged setae present in H. monticola ). Otherwise, males differ very distinctively from all remaining Asian Hydroscapha by the characters of the male sternites and genitalia mentioned above (see Table 2). Females are most similar to those of H. jumaloni in the combination of the rounded posterior margin of sternite VI and the medially projecting posterior margin of tergite VI, but are slightly larger.

Variation. Besides the variability of the body size and proportions of antennomeres (see Description), a slight variability of the shape of the aedeagus was observed in this species (Figs 3–6). The morphology of male abdominal sclerites of all specimens examined are, however, identical. For this reason, as well as because of the absence of any additional female morphotype at sampled localities, we consider the observed differences of the aedeagus shape as an intraspecific variability of H. khasiorum .

Etymology. We dedicate this species to the Khasi people from the Laitkynsew village, where the type series of this species was collected.

Distribution. The species is known from all three localities sampled for this study (see above), at which it was very common.