Thoracotropis Freeman, 1951 was described based on a single species from Chile – T. cypriformis – known from a single male specimen. The genus can be separated from other mycetophilids based on the reduced mouth parts, with two segmented palpus, and a some curious thoracic traits, as the mesonotum laterally compressed, quite strongly arched. Freeman (1951) included the genus in the Mycetophilidae "Leiini" (= Leiinae; e.g., Väisänen 1984; Matile 1993; Chan-dler 2009), a tribe encompassing 32 recent genera and almost 560 species worldwide (Edwards 1925; Hackman et al. 1988; Søli 1997; Kurina 2004; Oliveira & Amorim 2012). Thoracotropis has R 1 length less than twice r-m length (hence, longer than in other leiines and shorter than in other gnoristines) and a rather longitudinal r-m, two features used by Edwards (1925) to delimit Leiinae. A sinuous CuA (i.e., CuA 2 of Vockeroth 2009) has been also taken more recently as diag-nostic for the subfamily (Baxter & Poinar 1994; Jaschhof & Kallweit 2009). In a recent discussion about the limits of the Leiinae (Jaschhof & Kallweit 2009) Thoracotropis was con-sidered a leiine genus with a sinuous CuA. A detailed reexa-mination of the holotype of T. cypriformis, however, revealed that CuA is neither sinuous nor even slightly sinuous (Fig. 6), raising some doubts about its inclusion in the subfamily or at least in a higher clade of the Leiinae. Indeed, not all genera of Leiinae have the features pro-posed to be diagnostic for the subfamily. Actually, there is a recurrent discussion about the composition of the subfamily (e.g., Väisänen 1986; Søli 1997; Søli et al. 2000; Hippa et al. 2005; Jaschhof & Kallweit 2009). The problem of the mono-phyly of the Leiinae in a wider sense is being addressed in a phylogenetic study of the Leiinae (Oliveira & Amorim, un-published data). The purpose of this paper is to redescribe the holotype of Thoracotropis cypriformis, kept in the col-lection of the Natural History Museum, London (NHM) and to consider the problem of its inclusion in the Leiinae. METHODS