Hydrodessus latotibialis, Miller, Kelly B., 2016

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 : 87-90

Taxon classification Animalia Coleoptera Dytiscidae

Hydrodessus latotibialis sp. n. Figs 23, 42

Type locality.

Peru, Madre de Dios, Rio Tambopata Reserve, 30km SW Puerto Maldonado.

Diagnosis.

This species is part of a group including Hydrodessus maculatus , Hydrodessus phyllisae and Hydrodessus tenuatus that have the lateral elytral carina long (half or more the length of the elytron) (Fig. 23B), the prosternal process very broad (length/width <2) (Fig. 23C), and the metaventral platform (the region between the metaventrite carinae) conspicuously constricted near the base of the metaventral process and fairly broadly divergent posteriorly (Fig. 23C). Hydrodessus latotibialis differs from Hydrodessus maculatus in having the elytra red with only indistinct, weakly defined pale regions on the elytron (Fig. 23A) and from Hydrodessus tenuatus in having the pro- and mesotarsi broad with a subapical emargination (Fig. 7B). From Hydrodessus phyllisae , this species differs in size. Hydrodessus phyllisae are smaller (TL <2.7 mm) than Hydrodessus latotibialis (Tl> 2.9 mm). Also, specimens are more shiny than Hydrodessus phyllisae which are dorsally more matte. Unfortunately, male specimens of Hydrodessus latotibialis were not available, so the usually definitive male gentalia were not examined for comparison.

Description.

Measurements. TL = 3.0-3.2 mm, GW = 1.5 mm, PW = 1.2-1.3 mm, HW = 0.9 mm, EW = 0.5-0.6 mm, TL/GW = 2.0-2.1, HW/EW = 1.7. Body shape moderately robust, apically rounded, lateral margins distinctly discontinuous between pronotum and elytron (Fig. 23A).

Coloration (Fig. 23A). Head dark orange. Pronotum orange. Elytron dark orance with broad, indistinct pale areas anteriorly, subapically and at apex. Antennae, palps, and legs orange. Ventral surfaces dark orange.

Sculpture and structure. Head broad, anterior margin broadly rounded medially; surface covered with minute punctures; eyes moderately small. Pronotum subcordate, widest slightly anterior of middle (Fig. 23A); lateral bead fine; surface shiny with fine punctures. Elytra elongate, apically rounded (Fig. 23A); lateral carina extending posteriorly to about 1/2 length of elytron (Fig. 23B); surface shiny, covered with fine punctures. Prosternum medially carinate, setose; prosternal process moderately broad, subrectangular but widest at anterior laterally-expanded lobes, lateral margins slightly concave, subparallel, apex truncate, longitudinally strongly impressed (Fig. 23C). Metaventrite with anterior process moderately large, apically rounded, distinctly subapically constricted; metasternal carinae approximated anteriorly, posteriorly well-marked, strongly and evenly divergent across metasternum, ending near anterior terminus of metacoxal lines (Fig. 23C); other surfaces covered with fine punctures. Legs with most surfaces covered with fine punctures; metatibia with distinctive brush of dense, elongate setae on postero-apical surface; pro- and mesotibiae broad, with broad subapical emargination on dorsal margin (Fig. 7B); metatrochanter apically rounded but with small, sharp point; metacoxa evenly covered with fine punctures; metacoxal lines well developed, anteriorly slightly divergent but nearly subparallel (Fig. 23C). Abdomen shiny, evenly covered with fine punctures; apex of VI rounded.

Male genitalia. Only females were examined.

Female genitalia. Not examined.

Sexual dimorphism. Only females were examined.

Variation. No signficant variation was detected.

Etymology.

This species is named latotibialis from the Latin, lato, meaning “broad,” and tibialis, meaning “tibia,” for the relatively broad mesotibia in specimens.

Distribution.

This species is known only from one locality in Tambopata Reserve, Peru (Fig. 42).

Habitat.

The type specimens were collected from subtropical moist forest.

Discussion.

Two female specimens were examined of this species. Although ordinarily it is ill advised to describe new species of Dytiscidae based only on female specimens, this species appears sufficiently distinct that there should be little difficulty in associating specimens with this species in the future.

Specimens.

The holotype and one paratype were examined. The holotype female is in USNM labeled, "PERU: Madre de Dios: Rio Tambopata Res: 30 air km.SW Pto.Maldonado,290m 16-20 XI 1979 J.B.Heppner subtropical moist forest/ HYDRODESSUS sp. P.J.S. [handwritten]/ HOLOTYPE Hydrodessus latotibialis Miller, 2016 [red label with black line border]."

Paratype, 1 total. Peru, Madre de Dios, Rio Tambopata Reserve, 30km SW Puerto Maldonado, 290m, 16-20 Nov 1979, subtropical moist forest, J.B. Heppner (1, USNM).