Bidessonotus obtusatus Regimbart , 1895

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 : 110

Taxon classification Animalia Coleoptera Dytiscidae

Bidessonotus obtusatus Regimbart, 1895 Figs 1, 2, 22, 35

Bidessonotus obtusatus Régimbart, 1895: 336; J. Balfour-Browne 1947: 439; Young 1969: 2; 1990: 363; Biström 1988: 18; Nilsson 2016: 99.

Bidessus (Bidessonotus) obtusatus , Zimmermann 1920: 62.

Bidessus obtusatus , Blackwelder 1944: 76.

Diagnosis.

Specimens of this species are rather darkly colored with variable light markings that are usually conspicuous. The anterior clypeal margin is weakly sulcate and medially rounded. The prosternal process is relatively broad, flat and apically narrowly rounded. The male median lobe is diagnostic with the apical blade broadly truncate on the ventral margin, broad dorsally with a prominent obliquely truncate apicodorsal projection and the proximal margin with a small, irregular medial tooth and more well developed dorsal tooth (Fig. 22a,d). The right lateral lobe has the apical segment as long as the basal segment and is elongate and parallel sided and apically narrowly rounded (Fig. 22b). The left lateral lobe is much broader than the right, apically broadly concave with a distinct lobe along the ventral margin (Fig. 22c).

Discussion.

This is one of the commonest species in much of lowland South America with specimens collected especially from marshy lentic habitats and at lights. Young (1990) thought the species is related to Bidessonotus pollostus , Bidessonotus rubellus , Bidessonotus dubius and Bidessonotus ploterus .

Distribution.

Specimens have been collected from throughout lowland South America (Fig. 35). Young (1990) reported seeing hundreds of specimens from Argentina, Brazil, Bolivia, French Guiana, Colombia, Ecuador, Paraguay, Peru, Suriname, and Venezuela. The species is seemingly not as common as others in northern South America, but is present in lowland areas of Venezuela east to French Guiana.