How biologists determine what is or is not a distinct species is one of the more difficult problems in biology. This is especially true of cryptic species that are physically similar and differ only in the signals they use for mating behavior. Our research focuses on determining the possible existence of cryptic species in the leafhopper genus Erythroneura. There are 54 recognized species within this group of insects based on physical appearance. Most species live on redbud trees (Cercis canadensis) or grape plants (Vitis riparia). One species, Erythroneura comes, is an important pest of cultivated grapes and a few species are known to damage redbud. No studies have examined the mating behavior of any species in this genus. Our preliminary analysis of vibrational mating signals emitted by individuals from several populations in Indiana and Kentucky suggests that many unrecognized species may exist. Undergraduate students are involved in measuring variation in male mating signals and conducting mating experiments aimed at detecting and verifying the existence of these cryptic species.