Adults of a new taxon of Tomoplagia associated with the Asteraceae subtribe Lychnophorinae displayed body color variation. Allozyme electrophoresis was used to determine whether the dark and light morphs were cryptic species. Four loci clearly differentiated the light and dark morphs. The genetic identities and diversity (He) supported the hypothesis of cryptic species. A detailed morphological analysis also revealed consistent differences in the male and female terminalia of the two morphs. Based on these findings, we describe the dark morph as Tomoplagia reticulata sp. nov., and the light one as T. pallens sp. nov.