Wireworms are a common soil-dwelling pest of maize, Zea mays L., in the midwestern United States. Wireworms are a problematic group to control and study due to the difficulty involved in identification. The objectives of this study are to identify this species complex of wireworms by using molecular diagnostic techniques and to reconstruct a phylogeny of economically important wireworm species. The cytochrome oxidase I gene of mitochondrial DNA was sequenced from >300 individuals. The species analyzed include all economically important members of the genus Melanotus Eschscholtz as well as Conoderus lividus (De Geer). The species that are indistinguishable in the larval stage were successfully separated using nucleotide p-distances, and sequence data were then used in phylogenetic analyses. The data presented here represent an initial phylogenetic hypothesis concerning economically important wireworms. Our results indicate that the molecular phylogeny of the mitochondrial cytochrome oxidase subunit I gene provides a fast and accurate method of separating wireworm species. By increasing the ease and accuracy of identification, we hope to facilitate further investigations into their biology and control.