Limnogonus ignotus Drake & Harris, 1934

Limnogonus ignotus Drake & Harris, 1934: Ann. Carnegie Mus., 205–206.

Material examined. Galarza RS: 10 ♂, 10 ♀, flood-prone areas in Hermanos Fleita field, 18–19.iv.2013. Itatí RS: 1 ♂, Itatí marsh, Itatí Rincón Island, 28°42.73’S, 58°6.69’W, 29.iii.2014 ; 1 ♂, Estancia El Dorado, pond, 28°45.13’S, 58°7.40’W, 30.iii.2014 . Laguna Iberá RS: 1 ♀, route 40, roadside pond and ditches, 28°33’53.90’’S, 57°12’59.40’’W, 15.ii.2018; 1 ♂, route 40, roadside pond, 17.ii.2018. San Ignacio RS: 1 ♂, 2 ♀, vehicle path, roadside ditches, 27°54.444’S, 56°53.319’W, 3.iii.2015; 1 ♀, old pine tree forest of “ Las 600”, artificial channel, 27°51.834’S, 56°54.285’W, 5.iii.2015 . Yahaveré RS: 3 ♂, 2 ♀, Carambola Stream, 28°29’48.8”S, 57°41’09.6”W, 7.xi.2015 .

General distribution. Colombia, Venezuela, Guyana, Suriname, French Guiana, Brazil, Peru, Bolivia, Paraguay, Argentina, Uruguay (Damgaard et al. 2014; Motta et al. 2018; Morales et al. 2021).

Habitat. This species has been found in pools, ponds, lagoons, marshlands and ditches exposed to sunlight and with floating and emergent vegetation (Mazzucconi & Bachman 1995; Torres et al. 2007), stagnant pools along dry streams (Melo & Nieser 2004), and streams (Aristizábal-García 2002; Mazzucconi & Bachmann 2003). This pioneer species readily colonizes all kinds of stagnant waterbodies, including temporary, semipermanent, and artificial ones: rainwater accumulated in horse footprints, drinking troughs for livestock, swimming pools, and urban rain pools (Mazzucconi & Bachman 1995; Fontanarrosa et al. 2009).

At the INR, L. ignotus was collected from the margins of the Iberá Lagoon in shallow waters with emergent and floating vegetation (Estévez et al. 2003). During the present study, this species was collected on the water surface beside floating and emergent vegetation at the margins of lentic habitats (Itatí marsh, ponds and flood-prone areas) and lotic habitats in standing water (Carambola Stream, roadside ditches and artificial channels), mostly in unshaded areas.