Decarthrocerus mbizi, Perkins, 2009

Perkins, Philip D., 2009, Revisions of the genera Parhydraena Orchymont, Protozantaena Perkins, Decarthrocerus Orchymont, and Parhydraenopsis nomen novum, aquatic and humicolous beetles from Africa and Madagascar, and comparative morphology of the tribe Parhydraenini (Coleoptera: Hydraenidae), Zootaxa 2038, pp. 1-119 : 56

Decarthrocerus mbizi new species

( Figs. 88, 90, 103)

Type material. Holotype (male): Tanzania: S. W. Tanganyika, Mt. Mbizi , 12 mi. NE Sumbawanga , reserve forestiere, humus, elev. 2400–2600 m, 7° 51' S, 31° 43' E, vi.1960, N. Leleup. Deposited in the MRAC.

Differential diagnosis. This species is similar in habitus to D. jeanneli ; differing therefrom by the more explanate pronotum and elytra and the more convex pronotal relief and more convex elytra, and other more subtle differences ( Figs. 84, 88). The male genitalia of the two species differ markedly, and should be examined for reliable determinations ( Figs. 86, 90).

Description. Size (length/width, mm) holotype: body (length to elytral apices) 2.29/1.01; head 0.33/0.66; pronotum 0.52/0.91, PA 0.75, PB 0.67; elytra 1.47/1.01. Color brown to dark brown, lateral areas of pronotum lighter than disc; maxillary palpi light brown; dorsum with stiff, arcuate, yellow setae (dorsum usually thickly coated with debris).

Head with eyes small in dorsal aspect, ca. 6 convex facets in longest series. Ocelli almost indistinguishable, interocular foveae very small, narrow, shallow. Frons markedly concave laterally, hence eyes appearing elevated; cuticle dull, with granule at base of each arcuate seta, granules ca. 1xef or smaller. Frontoclypeal suture widely V-shaped. Clypeus with setae and granules like frons. Labrum dull, set at angle to clypeus, hidden in habitus view, apicomedially weakly emarginate. Maxillary palpi very short, combined lengths of meres much less than width of head (ratio ca. 15/44); ratios of meres 2–4 ca. 5/2/7. Mentum and submentum finely, densely punctulate, moderately setose, interstices shining.

Pronotum with anterior margin straight, median 2/5 with narrow hyaline border. Anterior angles obtuse, rather sharply rounded. Sides coarsely denticulate, rounded, widest past midlength, behind markedly attenuate, weakly emarginate. Posterior angle obtusangulate. Discal relief prominent, weakly shining, partially divided into two lobes by shallow posterior extension of anterior impression; granules ca. 1xef, separated by ca. 3–5xef. Anterior and posterior impressions deep, anterior extended posteriorly in midline, continuous with deep impression at each anterior angle; deep, wide impression at each posterior angle; granules in anterior and posterior discal impressions longitudinally elongate. Sculpture laterally sparsely granulate, weakly shining.

Elytra moderately shining, sides arcuate, markedly attenuate posteriorly; margins distinct from shoulder for ca. 5/7 of length. Ten-seriate punctate, punctures deep and large, on disc ca. 4xef or larger, separated by less than puncture diameter; each puncture with decumbent seta shorter and less erect than interval setae, no granule at base. Intervals shining, width ca. 1xpd, each with unilinear row of rather widely spaced, large, stiff, arcuate setae, most slightly larger than setae of pronotum.

Metaventrite with deep median elongate oval impression in posterior 1/2, strong midlongitudinal carina between anterior extreme of oval impression and mesoventral intercoxal process. Metaventrite and abdominal ventrites 1–4 hydrofuge pubescent. Apical abdominal segments elongate. Ventrite 5 slightly longitudinally convex, hydrofuge pubescent in basal 1/4, shining part pubescent in band across posterior 1/2; ventrite 6 simple, with sparse setae in posterior 1/2; last ventrite symmetrical, apex sharply rounded. Female unknown.

Legs moderately short, femora stout, tarsi very short, claws very small, combined lengths of metatibia and metatarsus slightly less than width of head (ratio ca. 41/44), ratio of lengths of metatibia/metatarsus ca. 30/11. Basal 3 tarsomeres markedly setose.

Wings fully developed in holotype.

Aedeagus length ca. 0.46 mm; main-piece apically pointed, markedly angulate in ventral view, angulate in lateral view, equally wide in proximal and distal 1/2, distal 1/2 bearing many long setae ( Fig. 90).

Etymology. Named in reference to the geographical distribution.

Distribution. Currently known only from the type locality in the Mbizi Mountains of Tanzania ( Fig. 103).