Exorista Meigen is one of the largest genera in the tribe Exoristini (Exoristinae) and comprises approximately 150 species worldwide. Most species are distributed in the Old World, with only six recorded in the Nearctic region (O'Hara & Wood 2004). Eight subgenera are currently recognized within the genus: Adenia Robineau-Desvoidy, Exorista Meigen, Exoristella Mesnil, Fauniodes Mesnil, Podotachina Brauer and Bergenstamm, Ptilotachina Brauer and Bergenstamm, Spixomyia Crosskey, and Thrycolyga Rondani. The monophyly of the genus Exorista and the phylogenetic relationships among subgenera are currently unclear.
Mesnil (1960) assigned many Exorista species of the Palearctic and Afrotropical regions into ten subgenera. Kugler (1980) added one monotypic subgenus from Israel to this genus. As mentioned above, eight subgenera are recognized at present and the remaining subgenera are treated as distinct genera or junior synonyms (Herting & Dely-Draskovits 1993). Chao (1964) and Liang and Chao (1992) described many Chinese species of Exorista, but some are possibly synonyms of other described species and the genus is in much need of revision in China (e.g. Crosskey 1976). Cantrell (1985) recorded 14 species from Australia, of which five were left unnamed. The Australian species were provisionally assigned to three subgenera with two species left unplaced.
Eleven species of Exorista, classified into five subgenera, are known in Japan: E. (Adenia) mimula (Meigen), E. (A.) tubigera Mesnil, E. (Exorista) japonica (Townsend), E. (E.) larvarum (Linnaeus), E. (Podotachina) sorbillans (Wiedemann), E. (Ptilotachina) xanthaspis (Wiedemann), E. (Spixomyia) aureifrons (Baranov), E. (S.) bisetosa Mesnil, E. (S.) cantans Mesnil, E. (S.) hyalipennis (Baranov), and E. (S.) patelliforceps Mesnil (Herting & Dely-Draskovits 1993). In the present study we add two species to the Japanese fauna: Exorista (A.) cuneata Herting and E. (Spixomyia) lepis Chao. Based on the morphological features of these species, together with those of some species from outside Japan, phylogenetic relationships between the subgenera are inferred. A key to the Japanese species is provided and diagnostic characters are illustrated.