In a lot of flies sent me from Illinois, by Professor S. A. Forbes, I find a most remarkable species, which I am satisfied must be located in the Syrphidæ, though the wing shows no sign of the spurious vein, and the first posterior cell is open. The third antennal joint bears a terminal arista, which character is shared by only two previously known North American genera; but the remarkable charater of the fly lies in its hind tarsi.