A new species-Docosia caucasica sp. n.-has been described from material collected from the Lesser Caucasus Mountains in Georgia (Sakartvelo). The new species belongs to a group of Palaearctic species characterized by distinct posterolateral processes of gonocoxites and apically modified setae at the posteroventral margin of the gonocoxites medially. Within the group, D. caucasica sp. n. is most similar to D. landrocki Laštovka and Ševčík, 2006 in having a similar outline of the medial process of posteroventral margin of the gonocoxites and the gonostylus. There is also a marked difference within the partial cytochrome c oxidase subunit 1 gene (COI) sequence of D. caucasica sp. n. and other Docosia spp. available in public databases. As the new species is described from a single male specimen only, the adequacy and code compliance of that are discussed.
Keywords: COI; Georgia; fungus gnats; new species; singleton; taxonomy.