Ochthebius (Aulacochthebius) nigeriensis, Perkins, 2023

Perkins, Philip D., 2023, Taxonomic revision of African water beetles in the genus Ochthebius Leach (1815) subgenus Aulacochthebius Kuwert (1887) (Coleoptera: Hydraenidae), Zootaxa 5228 (5), pp. 501-546 : 537

O. (Aulacochthebius) nigeriensis , new species

Figs. 2 , 4 , 19 , 28

Type Material. Holotype (male): “ NIGERIA: Oyo Prov., Ogbomosho , 12-13.ii.1949. B. Malkin coll.”; [8°8′N, 4°15′E] ( NHMUK) . Paratypes: Same data as holotype (12 NHMUK) .

Differential diagnosis. Differentiated from other similar members of the O. (A.) tenuipunctus Group by the combination of the slightly smaller size, and by the aedeagus. Very similar in characters to O. (A.) alienus and O. (A.) solitarius ; reliable determinations will require careful examination of the male genitalia.

Description. Size: holotype (length/width, mm): body 1.16/0.57 (length to elytral apices); head width 0.35; pronotum length 0.30, width at base 0.22, width at hyaline border 0.55, width of lateral sclerotized lobes 0.42 at anterior, 0.41 at posterior; elytra 0.76/0.57. Habitus as illustrated ( Fig. 19 ). Body longitudinally and transversely very convex. Dorsum brown to dark brown except hyaline borders of prothorax translucent. Eyes with moderately coarse, convex facets. Frons with deep impressions, borders of impressions rounded, smooth. Clypeus with very few, very shallow setigerous punctures. Labrum anterior margin arcuate.

Pronotal reliefs very smooth, with very sparse and very short setae; anterior and posterior transverse impressions deep, anterior contiguous with shallow transverse impression immediately behind anterior margin of lateral lobe; median longitudinal impression obsolete, almost imperceptible, only present at anterior transverse impression. Pronotum anterior margin bisinuate. Pronotum lateral hyaline borders very wide, extended from posterior to anterior angles, outer margin strongly arcuate; sides of non-hyaline part with long conspicuous setae immediately above and resting on hyaline border; anterior and posterior hyaline borders very narrow.

Elytra slightly wider than hyaline part of pronotum, posteriorly acuminate, sides markedly arcuate; very smooth, non-punctate, with sparse, very short, widely separated serial or subserial setae; lateral margin with very dense, very short setae that extend outward from margin in dry specimens

Abdominal venter ( Fig. 19 ): first four ventrites bearing rather long hydrofuge pubescence; remaining ventrites glabrous, shining, with sparse setae.

Etymology. Named in reference to the known distribution.

Distribution. Currently known only from Nigeria ( Fig. 28 ).

Figures

FIGURE 2. Dorsal habitus of species in O. (A.) tenuipunctus Group.

FIGURE 4. Venter and aedeagi (ventral view, flagellum deleted) of species in O. (A.) continentalis Group and O. (A.) tenuipunctus Group. Not to same scale.

FIGURE 19. O. (A.) nigeriensis n. sp., holotype habitus and aedeagus.

FIGURES 27–28. Geographical distributions. 27. O. (A.) species in Kenya and Uganda. 28. O. (A.) strangulatus Régimbart, O. (A.) tenuipunctus Régimbart and O. (A.) nigeriensis n. sp.