Nebrioporus kilimandjarensis ( Régimbart, 1906 )

Toledo, Mario, 2009, Revision in part of the genus Nebrioporus Régimbart, 1906, with emphasis on the N. laeviventris-group (Coleoptera: Dytiscidae), Zootaxa 2040, pp. 1-111 : 41-45

Nebrioporus kilimandjarensis ( Régimbart, 1906)

Figs 28, 65

Hydroporus (Nebrioporus) kilimandjarensis Régimbart (1906: 236) (orig. descr.); Zimmermann (1920: 133). Nebrioporus kilimandjarensis (Régimbart) ; Guignot (1956: 395; 1959a: 463).

Nebrioporus (s.str.) kilimandjarensis (Régimbart) ; Nilsson & Angus (1992: 287); Nilsson (2001: 173).

Type locality. Tanzania > Mount Kilimandjaro "Zone de forêts, torrents, vers 3500 mètres" .

Type material. Syntypes ( MNHN), coll. Alluaud and Peschet. Not studied .

Additional material examined. Tanzania: Kilimandjaro, 2050 m, 5.IX.1983, leg. P. Beron (3 exs. NMW, HF) ; "Africa or., Katona, Kilimandjaro " (5 exs. HNHM) ; " Afrique Or. Allemande, Kilimandjaro, versant sudest, Alluaud & Jeannel, Lisiére supér. Des foréts, Bismark-Hügel, 2700–2800 m, IV 1912 " (2 exs. IRSNB) .

Description. ML 7.3–7.8 mm; MW 3.3–3.4 mm. Unmistakable, large and dark species: the largest of the genus, and one of the largest known Hydroporinae. Oblong, convex, shiny, body outline interrupted by the narrow pronotum.

Head large, reddish-brown, widely darkened around the eyes and on the front. Mouthparts reddish, with last article of maxillary palps slightly darkened apically; antennae reddish with articles 4–11 apically darkened. Genae black.

Pronotum narrow, cordiform, maximum width near the anterior side, minimum width at its base. Sides almost straight, converging backwards, slightly rounded anteriorly (almost acute in females), distinctly bordered, posterior angles rounded. Angle between pronotum and elytra strong. A small, distal portion of scutellum is not concealed by the pronotum.

Elytra oblong, maximum width just above the middle of the length, lateral sides slightly rounded, strongly tapering to the apex. Longitudinal rows of punctures more or less visible. Subapical denticle present (see below in male and female characters).

Dorsal colouration ( Fig. 28a,b) mostly dark, pitch-black or dark-brown. On pronotum the dark colouration is composed by two large bands on anterior and posterior sides, and two large discal spots that could be very developed, leaving often just a vague paler border on the anterior and lateral sides. Elytra dark, with a series of paler and thin longitudinal vittae, often broken into spots.

Underside black, prosternal process and distal portion of sternites reddish or reddish-brown. Surface smooth and shiny. Punctuation composed by fine and diffuse punctures, poorly impressed, especially on sternites. Traces of a reticulation are hardly visible on sternites. Prosternal process flattened on proximal half, carinate on distal half. Sternites without comb of setae. Epipleuron reddish.

Legs reddish-yellow, with pro and mesotarsi darkened. Metatarsal segments darkened apically. Metatibiae with a long row of secondary setigerous punctures.

Male: Protarsi slightly dilated. Anterior claws ( Fig. 28d) modified, long and straight, slightly arcuate apically; the outer a bit longer than the inner. Median lobe of aedeagus ( Fig. 28f) dorsally elongate, with the tip slightly rounded; visibly sinuate in lateral view. Parameres ( Fig. 28e) strongly sclerotized, with ventral subapical margin protruding. Subapical denticles on elytra present, but bent downward, not protruding laterally, so that they are visible only in lateral view.

Female: Dorsal surface, especially on pronotum, duller, due to a more impressed microreticulation between the small and close punctures of the puncturation. Pronotum even narrower than in males ( Fig. 28b), with deeper angle between pronotum and elytra. Subapical denticles more developed ( Fig. 28c), bent downward but also visible in dorsal view.

Notes. N. kilimandjarensis is a spectacular case of allometry, in which diverse parts of its body have been abnormally modified, may be from a generic N. abyssinicus -like ancestor. This is suggested by some characters shared by both N. kilimandjarensis and some species of the N. abyssinicus -group, such as the shape of parameres and the tendency to reduce of the ventral puncturation. Specimens of N. abyssinicus from Tanzania are darker than Ethiopian populations, with females sharing often a very narrowed pronotum and elongated elytra (see above). At the light of this, it is possible to hypothesize that an isolated population has experimented an increase of size, together with a tendency towards an even narrower pronotum and more elongated elytra, ending up in the peculiar convexity of the body and position of the subapical denticle of N. kilimandjarensis . Nevertheless, no traces of anterolateral sinuations on elytra have been observed in this species, a character typical of members of the N. abyssinicus -group.

Distribution ( Fig. 56). Mount Kilimandjaro, apparently confined to mountain forests, up to 2000 m a.s.l.