A review of the fleas and lice of the Nearctic chipmunks indicates that North American chipmunks, Neotarnias and Tamias, have had separate histories; and that one has not been derived directly from the other. The western chipmunks (Neotarnias) have in common a species assemblage of sucking lice and fleas, and the single eastern species, Tamias striatus (Linnaeus, 1758), has distinctive species of fleas which do not generally occur on other small mammals; none of the lice or fleas on T. striatus occcurs on the western chipmunks. This dichotomy of distribution of external parasites on these chipmunks indicates a very long separation of the hosts, and could not occur if one group had been directly derived from the other. Chipmunks in western North America, on the basis of the molecular evidence and distribution of sucking lice and fleas, are most logically placed in the genus Neotarnias. Such an arrangement is consistent with the morphological, molecular, and parasitological evidence, and suggests a plausible history and relationship of the three groups of chipmunks. The fossil distribution of North American chipmunks indicates an early movement from Asia in the Oligocene, and a scarcity or absence of chipmunks from the middle Miocene until the Pleistocene. Both Tamias striatus and species of Neotarnias are probably a product of two Pleistocene movements across the Bering connection.
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