Ochthebius (Aulacochthebius) alienus, Orchymont

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 : 535

O. (Aulacochthebius) alienus Orchymont

Figs. 2 , 4 , 16 , 27

O. (Aulacochthebius) alienus Orchymont 1929: 196

Type locality: “ Afrique Orientale Anglaise ” (i.e., Kenya) .

Material examined (1): “ Kenya: Taita-Taveta Co., Ngulu swamp, Ipareni , Taita Hills , KEN 16-21, 3.4578S 38.3818E, 932m 22.I.2016; large marsh in agricultural area with sedges, 22.i.2016, leg. J. Bergsten & O. Bistrom ” (male, KNM) .

Differential diagnosis. Differentiated from other similar members of the O. (A.) tenuipunctus Group by the combination of the slightly larger size, the narrow band of very fine reticulation on each serial row of elytralpunctures; and by the aedeagus. Very similar in characters to O. (A.) nigeriensis and O. (A.) solitarius ; reliabledeterminations will require careful examination of the male genitalia.

Redescription. Size: specimen from Kenya (length/width, mm): body 1.25/0.65 (length to elytral apices); head width 0.40; pronotum length 0.30, width at base 0.26, width at hyaline border 0.57, width of lateral sclerotized lobes 0.46 at anterior, 0.44 at posterior; elytra 0.85/0.65. Habitus as illustrated ( Fig. 16 ). Body longitudinally andtransversely very convex. Dorsum dark brown, legs lighter, except hyaline borders of prothorax translucent to lightyellowish. 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 transverseimpressions deep, anterior contiguous with shallow transverse impression immediately behind anterior margin of lateral lobe; median longitudinal impression very shallow, extending from anterior transverse impression to ca. midlength. Pronotum anterior margin bisinuate. Pronotum lateral hyaline borders very wide, extended from posterior to anterior angles, outer margin markedly 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 wider than hyaline part of pronotum, posteriorly acuminate, sides markedly arcuate; very smooth, with serial rows of very shallow, widely spaced punctures, each with very short seta; each row with very narrow band of very fine reticulation; lateral margin with very long setae at and slightly behind humeral angle, otherwise margin with very dense, very short setae that extend outward from margin.

Venter: Tabella circular or slightly oval, convex; first four ventrites bearing rather long hydrofuge pubescence;remaining ventrites shining, with sparse setae.

Distribution. Currently known only from Kenya ( Fig. 27 ).

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 16. O. (A.) alienus Orchymont, habitus and aedeagus of specimen from Kenya.

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.