Hydraena (Hydraenopsis) mulanje, Bilton, 2023

Bilton, David T., 2023, New species and new records of minute moss beetles from East Africa (Coleoptera: Hydraenidae), Acta Entomologica Musei Nationalis Pragae 63 (1), pp. 103-110 : 106-107

Hydraena (Hydraenopsis) mulanje sp. nov.

( Figs 1–2 , 4 )

Type locality. Malawi, Mt. Mulanje, Ruo River Forest, 15°58′17.0″S 35°39′18.3″E, 970 m.

Type material. HOLOTYPE: J, labelled:“S MALAWI. Mulanje Mts./ Ruo river Forest / S15°58’17.0’’ E35°39’18.3’’ / 18-25.xi.2018, 970 / sifting P.Hlaváč lgt.” ( NMPC) with red holotype label . PARATYPES: 1 J 3 ♀♀, same data as Holotype; 1 ♀, labelled: “ MALAWI: Mt. Mulanje / Ruo river Forest, sifting, 970m / S15°58’17.0’’ E35°39’18.3’’ / 18-25.xi.2018, P.Hlaváč lgt.”, all with red paratype labels ( NMPC).

Description. Male. Colour. Dorsum ( Fig. 1B ) predominantly reddish brown; pronotum lighter than elytra except on parts of disc; head darkened posteriorly and almost black inside of compound eyes, legs light reddish brown; maxillary palpi yellowish brown; antennal stem segments pale yellowish brown, club somewhat darker; venter reddish brown to dark brown.

Head broadly triangular, broadest at posterior margin of eyes; narrowing abruptly in front of clypeus; narrowest at base of labrum. Compound eyes relatively large, occupying approximately 1/2 of side margin of head excluding labrum. Labrum transverse, deeply emarginate anteromedially, creating two rounded lateral lobes; lobes widest at base, labrum distinctly narrowed behind. Anterior and lateral margins slightly thickened and upturned, with short, curved setae. Upper surface of labrum dull, with fine microreticulation and scattered punctures bearing short, curved setae. Clypeus shining, with very sparse, short, curved setae; with weakly arcuate anterior margin, anterolateral angles obtuse; lateral margins slightly thickened, minutely serrate, with small, curved setae. Frontoclypeal suture indistinct, weakly arcuate. Frons much wider than clypeus, with front angles sharp and slightly obtuse; margins minutely serrate and setose in front of compound eyes; surface shining in centre, with dense, large, shallow punctures, bearing fine recumbent to decumbent setae; punctures in centre spaced 0.1–1 puncture diameter apart; closer towards inner margins of compound eyes, where cuticle has a somewhat rugose appearance. Maxillary palpi with palpomeres 3 and 4 somewhat expanded.

Pronotum transverse, cordiform, broadest just behind middle. Sides dentate, with smaller, curved setae; broadly rounded at broadest point, then weakly concave to posterior angles and weakly concave, then broadly rounded to anterior angles. Posterior angles pointed, weakly obtuse; anterior angles right angled. Anterior margin broadly emarginate in middle half, then almost straight to anterior angles. Posterior margin weakly bisinuate around centre and slightly recurved to posterior angles. Disc shining, devoid of microreticulation; with dense, large, shallow punctures bearing fine recumbent to decumbent setae; punctures larger than on head, spaced 0.1–2 puncture diameters apart. Pronotum weakly rugose towards lateral margins, particularly anteriorly. Anterolateral pronotal foveae shallow, transverse, open laterally; posterolateral pronotal foveae shallow, slightly elongate, continued to posterior margin.

Elytra broad, moderately elongate, widest close to middle. Sides weakly rounded to shallowly emarginated apex. Elytral margin broadly explanate, from just behind shoulder to close to apex; minutely serrate. Elytra shining, with 15 non-striate rows of large, shallow punctures, bearing long, fine recumbent setae, many lost; punctures larger and deeper than on pronotum. Elytral disc flat, gradually declining to apex over posterior half.

Venter. Mentum transverse, produced into broad triangular process apicomedially; anterior margins with dense suberect setae; lateral angles broadly rounded; surface shining, with sparse, fine punctures bearing long, fine recumbent to decumbent setae. Gena shining, without transverse ridges. Prosternal intercoxal process carinate, rugulosely sculptured. Pronotal hypomera broad, somewhat dull, with rugulose reticulation. Elytral epipleura broad, dull, isodiametrically microreticulate; continued almost to apex. Mesoventrite dull, strongly and rugulosely microreticulate, with dense setose vestiture; mesoventral intercoxal process parallel sided, lateral margins raised and shining. Metaventrite rugulosely punctured with dense vestiture and oval posteromedian depression; with short arcuate ridge on each side, extended posteriorly from margin of each mesocoxal cavity. Mesoventral plaques elongate ovals, flat, shining and slightly raised above rest of ventrite. Abdominal intercoxal sclerite width at arcuate posterior margin approx. 2× that of apex of mesoventral intercoxal process. Abdominal ventrites 1–4 slightly shining, with scale-like microreticulation and setose vestiture. Ventrite 5 shining in centre, with transverse microreticulation; vestiture restricted to anterolateral portions; apical margin broadly arcuate. Ventrite 6 shining, devoid of vestiture, with transverse reticulation; apical margin broadly arcuate. Ventrite 7 shining, with long, internal anteriorly directed processes bearing broad apical apodemes, supporting dense musculature. Last tergite with broad apicomedial notch.

Aedeagus ( Fig. 2B ) complex; main piece with an elongate process on right-hand side in ventral view, which is arcuate and paramere-like. Parameres attached just before mid-way on main piece; left paramere relatively large, with an expanded, setose apex; right paramere smaller, setae at right angles to shaft, left paramere partly obscured by angled process of main piece.

Female. Largely as males; maxillary palpi with segments 3 and 4 less expanded; abdominal ventrites 5–6 with straight apical margins; ventrite 6 with dense row of irregular puncture close to apical margin, bearing fine recumbent yellow setae.

Variation. Some variation in colour amongst the type series.

Measurements. Holotype BL = 1.65 mm; EL = 1.05; EW = 0.80 mm. Paratype male BL = 1.65 mm; EL = 1.10; EW = 0.80 mm. Paratype females BL = 1.65–1.70 mm; EL = 1.05–1.10 mm; EW = 0.80–0.85 mm.

Differential diagnosis. There are now 146 Hydraena known from the Afrotropical Region, of which only 50 are recorded from areas of tropical Africa south of the Sahara. Thirty-three of these were recently described from Cameroon by PERKINS (2022). Amongst known Afrotropical species, H. mulanje sp. nov. is readily distinguished by its broadly explanate elytral margins and aedeagal anatomy. The form of the aedeagus would apparently place the new species in Aedeagal Species Group 3 of Hydraenopsis Janssens, 1972 in PERKINS (2022), but the process adjacent to the right paramere is much larger in H. mulanje sp. nov. than in any of the described Cameroonian species.

Etymology. Named in reference to the type locality. The specific epithet is a noun in the nominative case.

Distribution and ecology. Known only from Mount Mulanje, an inselberg in southeast Malawi which reaches 3200 m, making it the highest mountain in the country ( Fig. 4 ). Specimens were collected from a forested ravine on the south side of the mountain where they were sifted from leaf litter. Apparently a terrestrial species.

Figures

Fig. 1. Malawi Hydraenidae, habitus. A – Coelometopon dedzae sp. nov.; B – Hydraena mulanje sp. nov.; C – Ochthebius erinaceus sp. nov.

Fig. 2. Malawi Hydraenidae, aedeagus, lateral and ventral views. A – Coelometopon dedzae sp. nov.; B – Hydraena mulanje sp. nov.; C – Ochthebius erinaceus sp. nov.

Fig. 4. Distribution map for taxa covered in this paper. Red circles indicate localities for Decarthrocerus jeanneli Orchymont, 1948 (bordered circle type locality).