The New World taxa related to Aemilia ambigua (Strecker) are revised and transferred to the genus Pseudohemihyalea Rego-Barros, resulting in the following nomenclatorial changes: Pseudohemihyalea ambigua comb. n., P. fallaciosa (Toulgoët) comb. n., and P. syracosia (Druce) stat. rev., comb n. Two Mexican species are newly described, P. sonorosa sp. nov., and P. potosi sp. nov. ''Aemilia'' carmen Schaus is also closely related to the ambigua-group, and is transferred to Pseudohemihyalea, comb. n. Like most species of Pseudohemihyalea, the ambigua species-group is restricted to southwestern North America and Central America. The forewing pattern and habitat association of the ambigua-group are likely the result of a novel larval host switch from broadleaf trees to pines (Pinus spp., Pinaceae). Adults and genitalia of all species are illustrated, except the female of P. potosi which is unknown. A key to the species of the ambigua-group is provided.