The adult male Scarlet-thighed Dacnis is unmistakable with a bright, turquoise-blue crown and nape, sides of head and neck, center of back, rump and scapulars. Its forehead, lores, sides of back, wings and tail, and mid-throat and belly are black; this is the only Dacnis that is black below. The thighs, for which this species gets its common name, are scarlet, but these are usually hidden. It is an inhabitant of forests, forest edges, shaded plantations, and isolated forest clearings. A social species, Scarlet-thighed Dacnis can be found in groups of up to 15 individuals, and also associates with mixed species foraging flocks. It has many common names in Spanish, as might be expected for such a beautiful bird, such as Dacnis Muslirrojo (Hilty 2011, de Juana et al. 2012), Mierlo Celeste y Negro (Stiles and Skutch 1989, Rodríguez Arias and Guido Granados 2012), Dacnis Musliescarlata (Iseli Troya and Proaño Freire 2012), and even Calzones Rojos in Costa Rica (Sandoval 2006). Other common names for the Scarlet-thighed Dacnis include Dacnis à Cuisses Rouges in French and Rotschenkelpitpit in German (Strewe 2003, Hilty 2011). The genus name Dacnis derives from the Greek word daknis, which refers to an unknown species of bird in Egypt mentioned by Hesychius and the grammarian Pompeius Festus (Jobling 2010). The species name venusta means lovely or beautiful (Jobling 2010).