Hydrodessus nanayensis Spangler, 1966

Miller, Kelly B., 2016, Revision of the Neotropical diving beetle genus Hydrodessus J. Balfour-Browne, 1953 (Coleoptera, Dytiscidae, Hydroporinae, Bidessini), ZooKeys 580, pp. 45-124 : 93-94

Taxon classification Animalia Coleoptera Dytiscidae

Hydrodessus nanayensis Spangler, 1966 Figs 3, 45

Hydrodessus nanayensis Spangler, 1966: 382; Young 1969: 2; 1970: 158; Spangler 1985: 89; Biström 1988: 37; Nilsson 2001: 236.

Type locality.

Peru, near Ituitos, from the Nanay.

Diagnosis.

This species is very similar to (or possibly identical with) Hydrodessus siolii . Putative differences based on information presented by Spangler (1966; 1985) include a more deeply impressed prosternal process, a more distinctly grooved medial metacoxal region (between the metacoxal lines) and a fasciate color pattern in Hydrodessus nanayensis (Fig. 3). Since the type specimen of Hydrodessus nanayensis was not examined, other potentially diagnostic features were unavailable.

Description.

Measurements. TL = 2.95 mm, GW = 1.35 mm. Body elongate, apically narrowly rounded, lateral outline distinctly discontinous between pronotum and elytron (Fig. 3).

Coloration (Fig. 3). Head and pronotum testaceous. Elytra testaceous except dark reddish-brown medial stripe along suture and three approximately transverse bands, one basal band extending across 2/3 elytral width, a medial band nearly reaching elytral margin and with elongate expansion medially narrowly separated from expansions of basal and apical bands, and apical maculate region (Fig. 3). Antennae, palps, legs and ventral surfaces testaceous.

Sculpture and structure. Head moderately broad, anterior clypeal margins arcuately emarginate; surface with fine, sparse, seta-bearing punctures, most dense between bases of eys, anterior portion nearly impunctate, microreticulate posterior to eyes. Pronotum cordate, widest near anterior margin (Fig. 3); lateral bead fine and distinct throughout length; surface with coarse, seta-bearing punctures separated by 1-2 × pore diameter, more coarse and dense near base. Elytra elongate, apically narrowly rounded (Fig. 3); lateral carina absent; surface finely alutaceous and densely, coarsely punctate, punctures separated by 1-2 × puncture diameter. Prosternal process slender between procoxae, width of apical portion about 2.5 × width between procoxae, weakly longitidinally concave. Legs alutaceous; metatrochanter somewhat swollen; metacoxa covered with coarse, dense, widely-spaced punctures. Abdomen with first abdominal ventrite with coarse, dense, widely-spaced punctures.

Male genitalia. Male unknown.

Female genitalia. Not described by Spangler (1966).

Sexual dimorphism. Male unknown.

Variation. Only a single female specimen has been described ( Spangler 1966).

Distribution.

This species is known only from the type locality near Iquitos, "from the Nanay," Peru (Fig. 45, Spangler 1966).

Habitat.

The single specimen was found "from the Nanay," which is a large tropical river, though it is not clear that the specimen was specifically collected from the river or, instead, from the region.

Discussion.

The specimen on which this species was based was collected during the Catherwood Foundation expedition to Peru. The type material was not found in either the Academy of Natural Sciences of Philadelphia (ANSP, where Spangler indicated the holotype was deposited, J. Weintraub, pers. comm.), the MZCZ (where many ANSP Coleoptera types were sent), or the USNM (where Spangler was working). The species was described from a single female specimen, and an illustration of the habitus was provided (Fig. 3). The description of the species is extensive, though it excludes certain important diagnostic features. The description presented here is based on Spangler’s (1966) description and his figure as well as later keys ( Spangler 1985; Young 1970). The shape of the beetle and the color pattern on the elytron are moderately distinctive (Fig. 3), and Hydrodessus nanayensis does not appear to correspond to any specimens examined during this study. The apparent loss of the type specimen or the fact that it is a female may make determining to what species this name refers difficult.

Young (1970) thought that Hydrodessus nanayensis is likely conspecific with Hydrodessus siolii , or, at most, a subspecies. The descriptions are very close and the shape and color pattern are very similar, but without examination of the type of Hydrodessus nanayensis , this cannot be determined conclusively.

Specimens.

No specimens were examined of this species, and the treatement here is based on the description by Spangler (1966).