Hydrodessus disjunctus, 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 : 71-74

Taxon classification Animalia Coleoptera Dytiscidae

Hydrodessus disjunctus sp. n. Figs 15, 42

Type locality.

Suriname, Sipaliwini District, Tafelberg Summit near Augustus Creek Camp, 3.933°N, 56.183°W.

Diagnosis.

This species is moderately elongate and dorsally and ventrally nearly concolorous red, without maculae on the elytra (Fig. 15A). The elytral apices are not dehiscent (Fig. 15A). The lateral elytral carinae extend about 1/4 length of elytron (Fig. 15B). The prosternal process is very broad and apically broadly truncate, broadly excavated medially, and slightly broader anteriorly (Fig. 15C). The metaventrite carinae are prominent, not medially constricted and posteriorly somewhat divergent, but the posterior apices are located distinctly mediad of the anterior apices of the metacoxal lines (Fig. 15C). The male median lobe in lateral aspect is relatively small basally with the apical portion slender, broadly and evenly curved (Fig. 15D). The apical portion is slightly constricted subapically, slender and pointed apically (Fig. 15D). The median lobe in ventral aspect is bilaterally symmetrical and slightly broadly expanded medially with the apical portion evenly convergent to moderately broadly pointed apex (Fig. 15E). The lateral lobe is moderately broad and with the lateral margins subparallel to the obliquely truncate apex which is somewhat, but distinctly, emarginate subapically (Fig. 15F). This species is most similar to Hydrodessus bimaculatus and Hydrodessus biguttatus . From Hydrodessus biguttatus it differs in the absence of dehiscent elytral apices and the shape of the male genitalia. From Hydrodessus bimaculatus this species differs in size ( Hydrodessus bimaculatus are longer, TL> 3.5 mm) and the male genitalia are different.

Description.

Measurements. TL = 2.7-2.8 mm, GW = 1.3-1.4 mm, PW = 1.1-1.2 mm, HW = 0.8 mm, EW = 0.4-0.5 mm, TL/GW = 2.1, HW/EW = 1.7. Body elongate, apically pointed, lateral outline distinctly discontinous between pronotum and elytron (Fig. 15A).

Coloration (Fig. 15A). Head and pronotum red to red-orange. Elytra evenly red with apex diffusely yellow (Fig. 15A). Antennae and palps red-yellow, antennomeres I–III darker red. Legs yellow-brown, metacoxa red-brown. Venter red, lighter red-yellow on head, prothorax, elytral epipleuron and apex of abdomen.

Sculpture and structure. Head broad, anterior clypeal margin broadly rounded, with fine marginal, flattened bead; surface shiny, microreticulate with few sparse punctures; eyes large. Pronotum subcordate, widest near anterior margin (Fig. 15A); lateral bead fine and distinct throughout length; surface shiny, covered with very fine, indistinct punctures, laterally somewhat rugose. Elytra elongate, apically pointed (Fig. 15A); lateral carina distinctive but short, extending about ¼ length of elytron (Fig. 15B); surface shiny with punctures very fine over entire surface, with one moderately impressed longitudinal line on disc. Prosternum medially somewhat swollen, rounded; prosternal process very broad, subquadrate, widest at anterior angles, deeply excavated medially, lateral carinate margins slightly convergent posteriorly, apex broad, broadly truncate (Fig. 15C). Metaventrite with anterior process broad, apically broadly rounded, medially flattened; metasternal carinae low and rounded but distinct, extending nearly across metasternum, lines constricted anteriorly, somewhat curved and slightly divergent posteriorly, terminating distinctly mediad of anterior ends of metacoxal lines (Fig. 15C); surfaces covered with fine punctures. Legs shiny, most surfaces with very fine, indistinct punctures; metatibia with posteroapical brush of setae distinctive; pro- and mesotibiae narrow; metatrochanter offset, apically rounded; metacoxa covered with fine punctures; metacoxal lines low and rounded, broadly separated, divergent anteriorly (Fig. 15C). Abdomen covered with fine punctures; VI apically broadly pointed.

Male genitalia. Median lobe bilaterally symmetrical, in lateral aspect narrow basally, slender and evenly and broadly curved, subapically slightly narrowed and curved to sharply pointed apex (Fig. 15D); in ventral aspect moderately narrow, lateral margins broadly curved, apically narrowly rounded (Fig. 15E). Lateral lobe broad basally, apically broad and straight, apically obliquely bilobed on dorsal margin, apex with dense fringe of setae (Fig. 15F).

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 no significant variation was discovered.

Etymology.

This species is named disjunctus, Latin for “separated,” for the distinctive distance separation between the posterior apices of the metaventrite carinae and the anterior apices of the metacoxal lines.

Distribution.

This species is known only from the type specimens from the Tafelberg in Sipaliwini District, Suriname (Fig. 42).

Habitat.

Specimens were collected from "forested creek margins."

Specimens.

The holotype male is in NZCS labeled, "SURINAME: Sipaliwini District N3°55.600', W56°11.300', 600m CSNR: Tafelberg Summit nr Augustus Creek Camp forested creek margins leg. Short & Bloom: 22.viii.2013 SR13-082202B/ SEMC1080468 KUNHM-ENT [barcode label]/ HOLOTYPE Hydrodessus disjunctus Miller, 2016 [red label with black line border]."

Paratype, 1 total. Suriname, Sipaliwini District, Tafelberg Summit near Augustus Creek Camp, 3.933°N, 56.183°W, 22 Aug 2013, forested creek margins, Short and Bloom (1, KUNHM, SEMC1080471).