A redescription of the genus Phalacropsylla Rothschild is provided. Six species are recognized: Phalacropsylla allos Wagner, P. hamata Tipton and Mendez, P. morlani Eads and Campos, P. nivalis Barrera and Traub, P. oregonensis Lewis and Maser, and P. paradisea Rothschild. Phalacropsylla hamata is designated herein as a junior synonym of P. paradisea. The distribution of P. paradisea is more extensive than previously thought, extending from Arizona through southern Colorado, into New Mexico, Texas, and northern Mexico (State of Nuevo León). It is the least host-specific of all species of Phalacropsylla, occurring on 13 different host species including cricetid, heteromyid, murid, and sciurid rodents and several carnivores, although it most commonly occurs on Neotoma albigula Hartley. The range of P. oregonensis is expanded from eastern Oregon to southeastern Idaho. Numerous records are documented for the most common and ubiquitous species, P. allos, which is found in British Columbia, central to northern California, Idaho, Montana, Colorado, Nevada, Utah, Wyoming, Arizona, and New Mexico. Neotoma cinerea Ord is the principal host of P. allos. Phalacropsylla allos is a winter flea west of the Rocky Mountains, but it has been reported in warmer months of the year on the eastern slopes of the Rocky Mountains in Larimer County, Colorado. A distribution map and key are provided for all species in the genus Phalacropsylla.
