Hypothyce mixta Howden, 1968 is endemic to sandy soils in east Texas, USA. Female H. mixta are not known to fly, raising the question of possible cryptic speciation due to lack of gene flow among geographically separated populations. There has been speculation that H. mixta is a taxonomically unrecognized cryptic species complex in which highly endemic populations have undergone sufficient genetic divergence over time to justify their recognition as separate species. The basis for this hypothesis was rooted in unpublished work on the mitochondrial CO1 gene that showed reciprocal monophyly among geographically distinct populations. A phylogenetic analysis of the nuclear gene 28S showed there is enough gene flow occurring between populations to maintain the singular species representation of H. mixta. However, there are distinct, minor morphological differences among populations, suggesting that this gene flow may be limited and that populations are diverging.