Bidessonotus spinosus Miller

Miller, Kelly B., 2016, New species of Bidessonotus Regimbart, 1895 with a review of the South American species (Coleoptera, Adephaga, Dytiscidae, Hydroporinae, Bidessini), ZooKeys 622, pp. 95-127 : 104-107

Taxon classification Animalia Coleoptera Dytiscidae

Bidessonotus spinosus Miller sp. n. Figs 10, 17, 30

Type locality.

Venezuela, Bolivar, Gran Sabana, Rio Aponwao at Rt 10, 5.847°N, 61.467°W.

Diagnosis.

Individuals have brown elytra with diffuse, poorly defined paler regions. The prosternal process is broadly oval, apically rounded and not sulcate. The female elytron has the apicolateral margin developed into a distinctive spine (Fig. 10b). The apical blade of the male median lobe is very broad with a spinous process at the anteroventral angle, a long, spinous process medially on the distal margin, and the dorsal margin irregularly subtruncate (Fig. 17a). The right lateral lobe has the apical segment broadly expanded along the ventral margin and about as long as the basal segment (Fig. 17b). The left lateral segment is shorter and broader with a distinct, rounded angulation along the ventral margin (Fig. 17c). The male genitalia (Fig. 17a,d) are similar to Bidessonotus truncatus (Fig. 28a,d) in having a distinctive spine along the apical margin. The apical blade is much broader and shorter with the proximal margin irregularly toothed (Fig. 17a,d).

Description.

Measurements. TL = 2.0 mm, GW = 1.0 mm, PW = 0.8-0.9 mm, HW = 0.6 mm, EW = 0.3 mm, TL/GW = 2.0, HW/EW = 1.7-1.8. Body shape elongate oval, lateral outline discontinuous between pronotum and elytron.

Coloration (Fig. 10). Head orange. Pronotum entirely yellow. Elytron base color brown with broad, diffuse, somewhat transverse slightly paler regions, margin of regions vague and indistinct (Fig. 10); without purplish dorsal iridescence. Prosternal surface yellow; other thoracic ventrites orange except metacoxa darker orange.

Sculpture and structure. Head with anterior clypeal margin slightly thickened laterally, broadly rounded; surface smooth and shiny; antennomeres III-X moderately broad, slightly asymmetrical. Pronotum widest near posterior angles, lateral margins evenly curved; basal striae moderately impressed, extending anteriorly more than halfway across surface; posterior margins distinctly undulate; surface overall shiny, surface mediad of striae slightly punctate. Elytron with lateral margins broadly curved; basal stria distinct, moderately elongate, well impressed basally; surface of elytron covered with punctation, surface between punctures shiny but with distinctive microreticulation. Prosternal process elongate, lanceolate, apically pointed, surface broadly convex throughout length. Metaventrite with carinae extending from medial apex of metaventrite process posteriorly to posterior margin at anterior terminus of metacoxal lines; lines narrowly separated anteriorly, slightly divergent posteriorly and somewhat effaced; surface of metaventrite shiny with few micropunctures. Metacoxa shiny with few micropunctures; metacoxal lines distinct, nearly parallel, width slightly increased near anterior margin making lines slightly undulate anteriorly. Basal abdominal ventrites punctate, other surfaces of abdominal ventrites smooth, relatively shiny.

Male genitalia. Apex of median lobe in lateral aspect with apical blade broad, with apicoventral sharp tooth, long spinous apicodorsal tooth, dorsal margin broadly subtruncate, proximal margin irregular (Fig. 17a). Right lateral lobe in lateral aspect with apical segment about as long as proximal segment; apical segment very broadly expanded with rounded lobe along ventral margin, apex broadly rounded (Fig. 17b); left lateral lobe lateral aspect with apical segment broader and shorter than right with distinct, angulate expansion along ventral margin (Fig. 17c).

Variation. The two specimens vary in the extent and intensity of the elytral fasciae and maculations.

Sexual dimorphism. With typical sexual dimorphism for Bidessonotus . Male with anteroapical margin of elytron evenly curved; female with anteroapical margin produced into small spine (Fig. 10b).

Etymology.

This species is named spinosus, Latin for “thorny,” for the long apical spine on the apex of the male median lobe.

Distribution.

Known from one locality in Bolivar State, Venezuela (Fig. 30).

Habitat.

Specimens were collected from a "small vegetated pool" and a "small streamlet."

Type material.

Holotype in MIZA, male labeled, "VENEZUELA: Bolivar State 6°50'49.2"N, 61°28.2'2.4"W, 1340m Rio Agonwao @ [sic] Hwy 10 31.vii.2008; leg. A.Short, M. García AS-08-060a; small vegetated pool/ SM0827643 KUNHM-ENT/ HOLOTYPE Bidessonotus spinosus Miller, 2016 [red label with red line border]." Paratypes, 1, Venezuela: Bolivar State, 6°50'49.2"N, 61°28.2'2.4"W, Rio Aponwao, 1340m, 31 Jul 2008, small streamlet, A. Short, M. García, legs., AS-08-060b, SM0830163.