Hydrodessus palus, 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 : 97

Taxon classification Animalia Coleoptera Dytiscidae

Hydrodessus palus sp. n. Figs 27, 42

Type locality.

Venezuela, Amazonas State, Communidad Cano Gato, Rio Sipapo, 4.981°N, 67.739°W.

Diagnosis.

This species has the lateral elytral carina relatively short, present just at the humeral angle (Fig. 27B), and the body overall nearly concolorous except somewhat darker on the apical half of the elytron (Fig. 27A). Hydrodessus palus is similar to Hydrodessus brevis in shape, and other structures, but that species is dark red (Fig. 12A) and Hydrodessus palus is pale yellow (Fig. 27A), and that species is a bit larger (TL = 2.5 mm) with Hydrodessus palus smaller (TL = 2.0 mm). The male genitalia differ, as well, with the median lobe of Hydrodessus palus more slender and apically sinuate (Fig. 27E).

Description.

Measurements. TL = 2.1-2.2 mm, GW = 0.8-0.9 mm, PW = 0.8 mm, HW = 0.6 mm, EW = 0.3 mm, TL/GW = 2.3, HW/EW = 1.9-2.0. Body very elongate, lateral margin distinctly discontinuous between pronotum and elytron (Fig. 27A).

Coloration (Fig. 27A). Body surfaces all yellow.

Sculpture and structure. Head broad, apically rounded; anterior clypeal margin broadly curved; surface with few, fine punctures; eyes large. Pronotum cordate, widest anterior to middle (Fig. 27A); lateral bead slender anteriorly, obscured posteriorly; surface shiny with fine punctures. Elytra elongate, laterally evenly rounded, apically pointed; lateral carina indistinct, rounded, present only near humeral angle (Fig. 27B); elytral surface shiny with fine punctation. Prosternum evenly rounded medially, weakly tectiform; prosternal process elongate, broad near base, extending laterally in rounded lobes, posteriorly slender, lateral carinae convergent posteriorly, medially longitudinally somewhat depressed, apex narrowly rounded (Fig. 27C). Metaventrite with anterior process slender, carinae not strongly developed, posteriorly diverging, represented by low, broad ridges ending near anterior ends of metacoxal lines (Fig. 27C); covered with irregular punctures. Legs with surfaces covered with fine punctures; pro- and mesotibiae moderately broad; metatrochanter strongly offset from metafemur, apex distinctly pointed; metatibia with posteroapical brush of setae; metacoxa covered with irregular punctures; metacoxal lines broadly separated, slightly curved, nearly straight, anteriorly slightly divergent (Fig. 27C). Abdomen covered with irregular punctation; abdominal ventrite VI apically evenly rounded.

Male genitalia. Median lobe bilaterally symmetrical, in lateral aspect somewhat curved, with basal portion narrowly triangular, apical portion very slender, broadly curved, apex slightly sinuate and narrowly pointed (Fig. 27D); in ventral aspect moderately slender, lateral margins broadly curved, constricted subapically with apex narrowly rounded (Fig. 27E). Lateral lobe moderately broad basally, long and elongate triangular with lateral margins evenly convergent to narrowly rounded apex which has a series of marginal setae (Fig. 27F).

Female genitalia. Not examined.

Sexual dimorphism. Male pro- and mesotarsi I–III more broadly expanded than female and ventrally with several large adhesive setae.

Variation. Only two specimens were examined, and there is no significant variation between them.

Etymology.

This species is named palus, Latin for “pale,” for the overall yellow coloration of specimens.

Distribution.

Hydrodessus palus is known only from the type locality in northwestern Amazonas, Venezuela (Fig. 42).

Habitat.

The two known specimens were collected from a sandy forest stream with considerable plant material (leaves, branches, etc) in the margins.

Specimens.

The male holotype specimen is in MIZA labeled, "VENEZUELA: Amazonas State 4°58.838'N, 67°44.341'W; 95m Communidad Caño Gato, on Rio Sipapo; 16.i.2009; leg. Short, Miller, Camacho, Joly, & García VZ09-0116-01X; along stream/ SM0842821 KUNHM-ENT [barcode label]/ HOLOTYPE Hydrodessus palus Miller, 2016 [red label with black line border]."

Paratypes, 1 total. Venezuela, Amazonas, Communidad Caño Gato, on Rio Sipapo, 4.980°N, 67.739°W, 16 Jan 2009, along stream, 95m, Short, Miller, Camacho, Joly, Garcia (1, KUNHM, SM0842840).