Hydrodessus laetus, 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 : 86-87

Taxon classification Animalia Coleoptera Dytiscidae

Hydrodessus laetus sp. n. Figs 22, 39, 51

Type locality.

Suriname, District Brokopondo, Brownsweg.

Diagnosis.

This species is robust and broadly rounded with a distinctive dorsal pattern of maculae and fasciae (Fig. 22A). The head and pronotum are yellow (Fig. 22A). The elytra are dark brown with yellow lateral margins and large, well-defined maculae subbasally, apically and at about 2/3 length of elytra (Fig. 22A). Specimens do not have a lateral elytral carina, the epipleural carina extends nearly straight from the humeral angle (Fig. 22B). The prosternal process is elongate oval with the apex broadly pointed (Fig. 22C). The metaventrite carinae are distinctive and moderately divergent posteriorly. The male median lobe is basally narrowly triangular (Fig. 22D). The apical portion is long and nearly evenly curved with the apex narrow (Fig. 22D). In ventral aspect the median lobe is bilaterally symmetrical with the lateral margins narrowed to narrowly rounded apex (Fig. 22E). The lateral lobe is elongate-triangular with a long series of setae along the dorsal margin (Fig. 22F). This species is similar to Hydrodessus rattanae in coloration, overall shape, lack of lateral elytral carinae, shape of the prosternal process and metasternum and other features. The male genitalia are diagnostic (Figs 22 D–F). Hydrodessus rattanae is also more robust, not as attenuate posteriorly and the color pattern is a little different. The metacoxal lines and regions mediad to the metacoxae are different, too. In Hydrodessus rattane the metacoxal lines are shorter, somewhat more divergent anteriorly and there are deep, longitudinal grooves along the medial margin of each metacoxal lines (Fig. 30C) that are missing in Hydrodessus laetus (Fig. 22).

Description.

Measurements. TL = 2.9-3.0 mm, GW = 1.4-1.5 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 broad, posteriorly pointed, outline discontinous between pronotum and elytron (Fig. 22A), body somewhat depressed.

Coloration (Fig. 22A). Head and pronotum yellow. Elytra fasciate, brown to brown-red with large irregular yellow regions transversely near anterior margin and medially, apex yellow, macula distinctly delimited (Fig. 22A). Antennae, palps and legs yellow. Ventral sclerites yellow, black along some sutures including metacoxal / abdominal sclerite I, abdominal I / II and the anterior metasternal margin.

Sculpture and structure. Head broad, anteriorly broadly rounded; surface shiny with fine mesh of reticulation and few, scattered, fine punctures; eyes large. Pronotum with lateral margins broadly rounded, widest slightly anterior to middle (Fig. 22A); lateral bead fine; surface shiny with fine microreticulation, covered with fine punctures. Elytra broad, lateral margins broadly curved, apically pointed; lateral carina absent, elytral epipleural carina extends directly posteriorly from humeral angle (Fig. 22B); surface with fine microreticulation throughout and covered with fine punctures. Prosternum medially tectiform; prosternal process broad, subrectangular, lateral margins broadly curved, apically broad and truncate, medially broadly excavated (Fig. 22C). Metaventrite with anterior process short and broad, medially distinctly excavated, slightly constricted subapically, apically subtruncate; metasternal carina distinctive, straight and diverging posteriorly, terminating at anterior ends of metacoxal lines (Fig. 22C); surfaces covered with fine punctation. Legs with surfaces shiny, weakly and indistinctly punctate; metatibia with posteroapical brush of setae distinctive; pro- and mesotibiae moderately broad; metatrochanter not strongly offset, elongate, apically narrowly rounded; metacoxa covered with fine punctation; metacoxal lines ro bust, well marked, broadly separated, subparallel but slightly divergent anteriorly (Fig. 22C). Abdomen covered with fine punctation; apex of VI narrowly rounded.

Male genitalia. Median lobe bilaterally symmetrical, in lateral aspect broadly and evenly curved, except apical 1/3 which is relatively straight, basal portion small and subtriangular, apical portion slender to narrowly rounded apex (Fig. 22D); in ventral aspect slender, lateral margins slightly curved, slightly narrowed medially and apex slender and narrowly rounded (Fig. 22E). Lateral lobe slender, elongate, without broad basal region, apex evenly narrowed to narrowly rounded apex (Fig. 22F).

Female genitalia. Gonocoxosternite broadly triangular, medial margin linear, apicolateral margin evenly curved, anterior portion large, broad, apically broadly rounded (Fig. 39). Gonocoxa elongate, apical portion elongate, apex narrowly rounded, medial margin curved, anterior apodeme long, as long as apical portion, slender (Fig. 39). Bursa bilaterally symmetrical, elongate slender, medially expanded, apically truncate; spermathecal duct extremely long and slender, expanded near receptacle which is semispherical; spermatheca bulbous with distinctive spermathecal spine; fertilization duct short and long (Fig. 39).

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

Variation. Specimens exhibit some minor variation in the extend of the maculae on the elytron.

Distribution.

This species is known from Venezuela (Fig. 51).

Habitat.

Specimens have been collected along a forest river and at lights.

Etymology.

This species is named laetus, Latin for “colorful,” for the attractive dorsal coloration of specimens.

Discussion.

See below under Hydrodessus rattanae for additional comments.

Specimens.

Holotype in MIZA labeled, "VENEZUELA,T.F.Amaz. Cerro de la Neblina Basecamp, 140 m. 0°50'N. 66°10'W 28 January 1985/ Netted along margin of Rio Baria P.J. & P.M Spangler, R.Faitoute.W.Steiner/ HOLOTYPE Hydrodessus laetus Miller, 2016 [red label with black line border]."

Paratypes, 5 total. Venezuela, Amazonas, Cerro de la Neblina, basecamp, 0.833°N, 66.167°W, 28 Jan 2985, netted along margins of Rio Baria, 140m, P.J. Spangler, P.M. Spangler, R. Faitoute and W. Steiner (2, USNM); same except 22 Feb 1985, blacklight in rainforest clearing near streams, 140m, P.J. Spangler, P.M. Spangler, R. Faitoute and W. Steiner (1, USNM); same except 6 Feb 2015, blacklight on bank of Rio Baria, 140m, W.E. Steiner (2, USNM).