Bidessonotus reductus 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 : 102-104

Taxon classification Animalia Coleoptera Dytiscidae

Bidessonotus reductus Miller sp. n. Figs 8, 15, 31

Type locality.

Venezuela, Bolivar State, Gran Sabana, N Santa Elena, Rio Guara at Rt. 10, 04°37.362'N, 61°05.679'W.

Diagnosis.

Specimens of this species are small and pale (Fig. 8). The prosternal process is lanceolate and slightly sulcate with the apex pointed. The male genitalia in the species are quite unique. The apical blade of the male median lobe is narrowed and elongate-triangular with the dorsal margin sharply pointed (Fig. 15a). The right lateral lobe has the apical portion very large and broad with a very broad expansion along the ventral margin (Fig. 15b). The right lateral lobe has the apical portion somewhat smaller relative to the basal segment but also broad and distinctly expanded along the ventral margin (Fig. 15c). Females have the apicolateral elytral margins unmodified.

Description.

Measurements. TL = 1.8-2.0 mm, GW = 0.9-1.0 mm, PW = 0.8 mm, HW = 0.5 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. 15). Head orange yellow. Pronotum yellow. Elytron base color light brown with diffuse, irregular pale fasciae, oriented more-or-less longitudinally, apex pale; female with indistinct purplish iridescence. Ventral surfaces yellow on all surfaces.

Sculpture and structure. Head with anterior clypeal margin evenly rounded; surface smooth and shiny, with few micropunctures medially; antennomeres III-X moderately broad, slightly asymmetrical. Pronotum widest near posterior angles, lateral margins evenly curved; basal striae distinctly impressed, especially basally, elongate, extending anteriorly more than halfway across surface; posterior margins distinctly undulate; surface shiny, medial surface finely punctate. Elytron with lateral margins broadly curved; basal stria distinct, elongate, well impressed; surface of elytron covered with fine punctation, surface between punctures somewhat shiny but microreticulate. Prosternal process moderately broad, broadly oval, apex rounded, surface broadly convex throughout length. Metaventrite with distinctive carinae extending from medial apex of metaventrite process posteriorly to near posterior margin at anterior terminus of metacoxal lines; anteriorly very closely approximated, strongly divergent to posterior margin; surface of metaventrite shiny, impunctate. Metacoxae shiny, nearly impunctate; metacoxal lines distinct, broadly separated, anteriorly slightly divergent. Abdominal ventrites smooth, relatively shiny.

Male genitalia. Apex of median lobe in lateral aspect with blade reduced, slender, sharply pointed at dorsal margin (Fig. 15a). Right lateral lobe in lateral aspect with apical segment much longer than proximal segment; apical segment apically very broadly expanded medially, apex broadly rounded (Fig. 15b); left lateral lobe with apical segment shorter than basal segment, broad with apex truncate and with distinct expansion along ventral margin (Fig. 15c).

Variation. The two specimens vary somwhat in the extent and intensity of the pale elytral areas.

Sexual dimorphism. Specimens of this species with typical Bidessonotus sexual dimorphism and female more matte dorsally than male. Without other evident dimorphisms.

Etymology.

This species is named reductus, Latin for “reduced,” for the relatively small apical blade of the male median lobe.

Distribution.

Known only from the Gran Sabana, Bolivar State, Venezuela (Fig. 31).

Habitat.

Specimens have been collected from "marshy areas."

Type material.

Holotype in MIZA, male labeled, "VENEZUELA: Bolivar State 04°37.362'N, 61°05.679'W, 876 m Gran Sabana, N. Santa Elena Rio Guara at Rt. 10. 17.VII.2010 Leg. Short, Tellez & Arias marshy area; VZ10-0717-02A/ SEMC0908509 KUNHM-ENT [barcode label]/ HOLOTYPE Bidessonotus reductus Miller, 2016 [red label with double black line border]." Paratype, 1 female, Venezuela, Bolivar State, 04°41.878'N, 61°04.246'W, 815m, Gran Sabana, N Santa Elena, marshy area along Rt 10, Short, Tellez and Camacho, legs. 17 Jul 2010, VZ10-0717-03A, SEMC0908642.