Elachistocleis bicolor, the two colored oval frog, is a South American microhylid species that lives buried in leaf litter on low forest floors and grasslands (up to 200 m asl). As it can tolerate some disturbance it can also be found in urban and rural gardens. The nocturnal adults feed mostly on ants.Aquatic larvae hatch from eggs laid in quiet pools; the eggs float on the water surface (Lavilla et al. 2004).Williams and Gudynas (1987) described the tadpoles as similar to those of E. ovalis and E. surinamensis: globular, cryptically colored, with small eyes and about 24 mm in length.
Elachistocleis bicolor is long-set in taxonomic confusion with the oval frog, Elachistocleis ovalis. Variation in morphological and behavioral characters used to define species across the enormous range have made species differentiation extremely difficult. Recently, Brusquetti and Lavilla 2006 (cited in Frost 2015) and Lavilla et al. 2003 operationally defined E. bicolor as Elachistocleis frogs with no black patterning (immaculate) on their ventral surface and occurring south of the Amazon River: in Central Argentina and Uruguay through Paraguay to southern Brazil (Frost 2015; Lavilla et al. 2003). No named types or type localities exist, but literature digging reported by Lavilla et al. (2003) indicates that Buenos Aires is the likely type location for the two specimens collected and named in 1838.Similarly, Lavilla et al. (2003) define E. ovalis as having an immaculate ventrum, but occurring in the northern part of the range.They strongly caution that both names almost certainly consist of species complexes. Multiple new Elachistocleis species have been recently defined (e.g. Caramaschi 2010; Nunes-De-Almeida 2012; Pereyra et al. 2013; Toledo 2010) and more will certainly follow, so this taxonomy serves as scaffold for future revision, perhaps employing molecular methods (Lavilla et al. 2008; Brusquetti and Lavilla 2006).
