A number of species of Argidae were proposed in the late 1800s and early 1900s, all of which later were regarded as a single color-variable species, Schizocerella pilicornis (Holmgren). In the mid-1970s, an external-feeding type was reported in the literature, and it also was identified as S. pilicornis, although previously S. pilicornis was only known to feed by leaf mining. Thus, the uniqueness of a species with two distinct feeding types led us to question the taxonomy of S. pilicornis. We use data from the mitochondrial cytochrome oxidase I gene (COI) to show that the two feeding types have a sequence divergence of 5.8%, which exceeds the difference between many insect taxa currently classified as different species. Considering the existing evidence on morphological, behavioral, allozymic, and ecological differences, we here recognize these two feeding types as distinct species: Schizocerella pilicornis (Holmgren) as the leaf-mining species and Schizocerella lineata (Rohwer) as the external-feeding species. We provide a diagnosis for each species, and show that adults of S. pilicornis have a mostly black mesonotum, whereas adults of S. lineata have an orange–red mesonotum.