Hydrodessus spanus Spangler, 1985

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 : 108-109

Taxon classification Animalia Coleoptera Dytiscidae

Hydrodessus spanus Spangler, 1985 Figs 32, 44

Hydrodessus spanus Spangler, 1985: 83; Biström 1988: 37; Nilsson 2001: 236.

Type locality.

Guyana, Mazaruni-Potaro District, Takutu Mountains, 6°15'N 59°5'W.

Diagnosis.

This species has the elytron red with a moderately well-defined yellow macula at about 2/3 length of elytron (Fig. 32A). The pronotum is yellow and lighter in color than the elytron (Fig. 32A). The lateral carina on the elytron is low and rounded and mainly evident only near the humeral angle (Fig. 32B). The prosternal process is moderately narrow with the lateral carinae somewhat constricted medially and the apex rounded (Fig. 32C). The metaventrite carinae are only moderately distinct and clearly divergent posteriorly (Fig. 32C). The species is sexually dimorphic. Females have the anterolateral margin of the elytron flanged, unlike males. Females also have distinctive impressions on each side of abdominal ventrite VI. The male median lobe in lateral aspect is elongate triangular basally with the apical portion elongate, slender and curved with the apex distinctly sinuate and with a distinct angulation along the ventral margin subapically (Fig. 32D). In ventral aspect the apex is broadly rounded with distinct lateral teeth (Fig. 32E).

Description.

Measurements. TL = 2.7-2.8 mm, GW = 1.3 mm, PW = 1.1-1.3 mm, HW = 0.8-1.1 mm, EW = 0.5-0.8 mm, TL/GW = 2.1, HW/EW = 1.6-1.9. Body moderately robust, apically broadly pointed, lateral outline distinctly discontinuous between pronotum and elytron (Fig. 32A).

Coloration (Fig. 32A). Head brown, lighter posterolaterally and on clypeus. Pronotum yellow. Elytra brown to dark brown with submedial diffuse pale area and apex pale (Fig. 32A). Antennae and palps yellow. Legs yellow, dark red on ventral margins of femora. Venter dark red-black medially on prosternum, prosternal process, metasternum, metacoxae, abdominal ventrites, lighter laterally, becoming red to red-yellow on pronotal and elytral epipleura and laterally and apically on abdomen.

Sculpture and structure. Head broad, anterior clypeal margin broadly curved; surface shiny, covered with fine punctures; eyes moderately large. Pronotum subcordate, widest anterior of middle (Fig. 32A); lateral bead continuous and fine; surface with fine punctation, laterally with irregular rugosity. Elytra moderately elongate, apex broadly pointed (Fig. 32A); lateral carina low and rounded and only evident near humeral angle (Fig. 32B); surface covered with fine punctation. Prosternum medially tectiform and setose; prosternal process elongate, lateral margins distinctly constricted medially, shallowly impressed longitudinally, apex rounded (Fig. 32C). Metasternal process with apex truncated, medially flattened, subapically laterally constricted; metasternal carinae distinctive only along anterior process, extending posteriorly as line of impunctate surface (Fig. 32C); other surfaces covered with fine punctation. Legs covered with fine punctures on most surfaces; metatibia with distinctive brush of dense, elongate setae on postero-apical surface; pro- and mesotibiae moderately broad; metatrochanter distinctly offset, apically narrowly rounded; metacoxa evenly covered with fine punctures; metacoxal lines broadly separated, slightly curved, anteriorly somewhat divergent (Fig. 32C). Abdomen evenly covered with fine punctures; apex of VI slightly bisinuate, medially broadly pointed.

Male genitalia. Median lobe bilaterally symmetrical, in lateral aspect strongly and broadly curved, with basal region short and robust, apical portion strongly constricted, apically subsinuate, subapically slightly expanded and apex pointed (Fig. 32D); in ventral aspect robust and broad, lateral margins slightly curved and slightly divergent to broadly rounded, abruptly expanded apex (Fig. 32E). Lateral lobe basally broad, apical portion elongate triangular, apex broadly sub-truncate, apicodorsal margin with series of setae (Fig. 32F).

Female genitalia. Not examined

Sexual dimorphism. Male pro- and mesotarsi I–III more broadly expanded than female and ventrally with several large adhesive setae; female with elytron prominently expanded and lobate subapically, male evenly curved; male abdominal seternite VI evenly rounded across surface, apex with minute pointed lobe apically, female with prominent lateral depression on each side of VI.

Variation. Few specimens were examined, but they vary somewhat in the intensity of coloration.

Distribution.

Hydrodessus spanus are known from Guyana, Suriname and southeastern Venezuela (Fig. 44).

Habitat.

Specimens have been collected at a blacklight in a forest clearing near streams.

Specimens.

The holotype male in USNM was examined, labeled, "GUYANA: Mazaruni- Potaro District Takutu Mountains 6°15'N, 59°5'W 17 December 1983/ EARTHWATCH Research Expedition: P. J. Spangler & W. E. Steiner Collectors/ At blacklight in forest clearing near streams/ HOLOTYPE Hydrodessus spanus PJ Spangler [red label]/ BLNO 003807 [blue label with black line around margin]."

Other non-type specimens examined, 3 total. Suriname, Sipaliwini District, Camp 1, Upper Palumeu, 2.175°N, 56.787°W, 19 Aug 2010, UV light, 228m, A.E.Z. Short (1, KUNHM, SEMC0914432). Venezuela, Bolivar, 85km SEE Dorado, 6.085°N, 61.399°W, 1 Nov 1982, E. Rubio, T. Borrego (1, KUNHM); Bolivar, San Ignacio, 9.567°N, 64.500°W, 8 Sep 1977, 1000m, B. Bechyne (1, MIZA, MIZA0001487).