Diabrotica virgifera zeae Krysan and Smith n. ssp. is described and the geographic distribution of D. virgifera LeConte is given. Conspecificity of the 2 subspecies is indicated by morphological similarity, geographic distribution, intermediate phenotypes, and the results of laboratory studies of mating choice and male competitiveness and field experiments on responses to pheromones. Characters distinguishing the 2 subspecies from each other and from D. longicornis (Say), a close relative, are described and included in a key.