Belostoma bachmanni De Carlo, 1956

(Figs. 3D, 10A)

Known distribution: Known only from the locality of the type series (Paraguay, Department. Concepción, Puerto Vallemí) (De Carlo, 1956) and from Brazil, Purus river and Solimões river (Estévez, unpublished data).

Material examined: 3 females, ethyl alcohol 70%, BRAZIL, Amazonas, Novo Airão municipality, Anavilhanas National Park, 01.IX.2001, G. Machado coll., F. Stefanello, 2018 det .; 1 male and 2 females, ethyl alcohol 70%, São Gabriel da Cachoeira municipality, 07.VIII.2010, R. L. Ferreira-Keppler & S. R. S. Torreias coll., F. Stefanello, 2018 det .; 1 male and 2 females, ethyl alcohol 70%, Barcelos municipality, Aracá river, 00°24’13.8”S 62°55’57.6”W, 25.IX.2014, A.M.O. Pes et al. colls., F. Stefanello, 2018 det .; 1 male, ethyl alcohol 70%, Santa Isabel do Rio Negro municipality, Jaradi stream, 00°20’14.2”S 65°12’25.7”W, 18.IX.2014. A.M.O. Pes et al. colls., F. Stefanello, 2018 det .; 4 males and 6 females, ethyl alcohol 70%, Maruiá river, 19.IX.2014. A.M.O. Pes et al. colls., F. Stefanello, 2018 det .

Notes: This species is poorly cited in the literature and unknown by many researchers studying giant water bugs. There were doubts about which species group Belostoma bachmanni belongs to and its range of distribution. Recently, Estévez (unpublished data) included this species in the B. triangulum group of Lauck (1964), considering the triangular prosternal keel and male genitalia, which have arms of phalobase long, extending beyond the flat ventral diverticulum. The males examined were 19.5-20.0 mm in length and the greatest body width were 9.6-10.2 mm; females were 19.8-21.0 mm in length and the greatest body width were 9.5-10.2 mm, both male and female have flattened body. This species appears to be relatively abundant along the Negro river and its tributaries.