Shannon's “Revision of the Chilosinae” includes keys to the species of the various genera of the group but in some cases no descriptiolls of the new species are included. In the key to Cartosyrphus the characters separating some closely related species are difficult to interpret. The male of C. similis Shan. is separated from tristis Lw. by the slightly more swollen first segment of the posterior tarsi. While this character is quite satisfactory in the female it cannot be relied upon in the male. In order to verify observations made several years ago when I compared specimens with the types of the two species mentioned I wrote to Dr. Banlis requesting information on the colour of the squamal cilia.