The Seychelles archipelago is characterized by an exceptionally high level of endemism in certain taxa, including at least 275 endemic species of Lepidoptera (Legrand 1966; Gerlach & Matyot 2006; De Prins & De Prins 2015). Despite the fact that endemics are the main objects of conservation efforts, information regarding endemic Seychelles Lepidoptera is very poor, because the majority of them are known from a single or a few specimens (Legrand 1966; Gerlach and Matyot 2006; Bolotov et al. 2014, 2015). The emerald moth specimens are lacking in extensive samples obtained by earlier collectors (Fletcher 1910; Scott 1910; Fryer 1912). Further, two emerald moth species in the genus Thalassodes Guenée, 1858 have been reported from Seychelles, i.e., the widespread T. quadraria Guenée, 1858 (Legrand 1966; Gerlach & Matyot 2006; De Prins & De Prins 2015) and the endemic T. antithetica Herbulot, 1962. The latter species is known from eight specimens, collected between 1959 and 1963 (Legrand 1966; Gerlach & Matyot 2006). Herbulot (1962) provided a very short description of this species without any illustration. The protologue consists of a description of some external characters, i.e., antennae, palpi and legs, as well as the pattern of markings, but the male and female genitalia are not described. As the main diagnostic features, Herbulot (1962) noted two specific characters in the male morphology, namely the hind tibia with a single pair of spurs and an exceptional development of the lateral processes (octavals) on the posterior margin of the eighth sternite.