Agabus joachimschmidti, Brancucci, Michel & Hendrich, Lars, 2008

Brancucci, Michel & Hendrich, Lars, 2008, 5100 m above sea level: Agabus joachimschmidti sp. n. and notes on other high altitude diving beetles from Tibet and Bhutan (Coleoptera, Dytiscidae), Zootaxa 1825, pp. 51-58 : 52-54

Agabus joachimschmidti sp. n.

Figs 1–5

Type locality. Small spring, Budha Valley N of Yangpachem, Tibet South Central.

Type material studied. Holotype male ( NMB): “ TIBET South Central, Budha Valley N of Yangpachem, about 30°10'38 N 90°30' 18E, 20.VI.2007, 5100m ” [white printed label]. “ Holotype Agabus joachimschmidti sp.n. Brancucci & Hendrich des. 2008” [red printed label]. Paratypes: 9 specimens with same data as holotype (3 males and 4 females NMB, 1 male and 1 female CLH). All specimens are provided with a red printed paratype label.

Description. Measurements: Holotype: total length = 6.20 mm, total length-head = 5.60 mm, total width = 3.20 mm. Paratypes (male and female do not differ in size): total length = 5.60–6.10 mm (5.85 mm, n = 7), total length-head = 5.20–5.50 mm (5.35 mm, n = 7), total width = 2.90–3.20 mm (3.08 mm, n = 4).

Habitus: Body short-oval, distinctly convex, black on head and pronotum and dark brown on elytra ( Fig. 1 ).

Head: Black, shining, labrum testaceous. Antennae testaceous at base, becoming darker brown on distal part from the 4th joint on. Reticulation consisting of medium-sized and well-impressed polygonal meshes, irregular in size, with a small puncture on the inner side of some meshes. Row of punctures alongside eyes and clypeal grooves well-impressed. A few punctures beside eyes well-impressed but not confluent. Antennae short, joints almost globose, the 5th only 1.2 times as long as broad.

Pronotum: Black, shining. Reticulation consisting of polygonal meshes, irregular in size and often incomplete particularly on disc; some meshes with 1 very minute puncture, seldom more, on their inner surfaces. Latero-basal part with few deep wrinkles. Anterior row of punctures complete; punctures very large, confluent and in groups, leaving small spaces free. Posterior row broadly interrupted at middle; punctures large, irregularly distributed, confluent at sides. Lateral margin distinctly bordered with punctures alongside the grooves. Sides of pronotum rather straight, forming a distinct pronoto-elytral angle, base of pronotum narrower than base of elytra ( Fig. 1 ).

Elytra: Brownish-black with a distinct bronze lustre. Epipleura brown. Reticulation consisting of wellimpressed polygonal meshes, with one minute puncture on the inner side of some meshes. Sutural row of punctures restricted to apical two-thirds and consisting of some medium-sized well-spaced punctures. Discal, sublateral and lateral rows not reaching base; punctures well-spaced, here and there in groups. Punctures present in interspaces between discal and sublateral rows. Epipleura broad at base, strongly narrowed by first sternite and evenly but slightly tapered as far as apical part.

Venter: Dark ferrugineous-brown, legs testaceous, femora dark brown. Prosternal process lanceolate, very narrow and strongly convex. Metacoxal line complete. Metafemora with a short row of setae, slightly transversely reticulated. Metatibiae with two rows of punctures, one along outer margin and consisting of 7–9 larger punctures each with a strong but short seta, other along inner margin, shortened distally with 4–5 large punctures; ground-surface distinctly shining.

Sexual dimorphism: Male with protarsi and mesotarsi distinctly dilated, with numerous small rounded pads. Protarsal and mesotarsal claws almost as long as protarsomere 5 and mesotarsomere 5, respectively. Anal sternite microreticulate on anterior third, somewhat wrinkled and punctured on posterior half. Posterior margin distinctly flattened, finely bordered. Median lobe of aedeagus, in lateral view, regularly curved, bidentate in apical part ( Fig. 3 ); in dorsal view, suddenly tapered and prolonged into a sharp point at apex. Basal part of parameres short but narrow ( Fig. 5 ). Female similar to male. Anal sternite distinctly reticulate on posterior half, with coarse and irregularly distributed punctures on both sides of middle. Protarsal and mesotarsal claws only 1.4 and 1.3 times shorter than protarsomere 5 and mesotarsomere 5.

Derivatio nominis. Dedicated to Joachim Schmidt (Admannshagen, Germany) a well-known specialist of Himalayan ground beetles.

Differential diagnosis. This species clearly belongs to the confinis -group as delimited by Nilsson (1990, 2001), mainly characterized by a bifid median lobe and a typical habitus of the species. It is related to A. tibetanus , but can be easily distinguished by its smaller size. The total length is 5.85 mm as the mean between all paratypes, whereas it is 6.8 mm in A. tibetanus . The sides of the pronotum are rather straight and not regularly rounded, forming a distinct pronoto-elytral angle, the base of the pronotum being narrower than base of elytra ( Fig. 1 ); in A. tibetanus , the base of pronotum and the base of elytra are approximately of the same width ( Fig 2 ). The posterior enlarged part of the metacoxal processes is provided laterally just with a few larger punctures, whereas it is distinctly bordered in A. tibetanus . The sutural rows of the elytra are incomplete and just marked by a few larger and sparse punctures, but are complete and very distinct in A. tibetanus according to the re-description by Nilsson (1990). Finally, the anal sternite is less roughly puncturate and wrinkled. The median lobe of aedeagus does not allow a clear identification to be made, but the subapical tooth is more elongate ( Figs 3 & 4 ).

Habitat. These specimens were collected at an altitude of 5100 m, which may be an altitude record for dytiscids. The habitat was a flat area of debris with water trickling over it, with the source exposed to the south. This appears to be a temporary habitat as the ice-free period at this altitude seems to be quite short.

Distribution. Only known from the type locality but probably more widespread in south central Tibet.

Figures

FIGURES 1 – 5. Habitus of: 1) Agabus joachimschmidti sp. n., 2) A. tibetanus; median lobe of aedeagus in lateral view of: 3) A. joachimschmidti sp. n., 4) A. tibetanus; 5) right paramere of A. joachimschmidti sp. n.