Several kinds of fleas do not belong in either of the above groups. Some fleas were accidental strays from mammals not included in table 6; and one flea (_Rectofrontia fraterna_) may prove to be a common nest parasite. _Orchopeas howardii_ is common on tree squirrels (_Sciurus niger_ and _S. carolinensis_). _Nosopsyllus fasciatus_ is a cosmopolitan flea on _Rattus norvegicus_. _Rectofrontia fraterna_ was taken once from a prairie vole. Since the only specimens in the University of Kansas Entomological Collections are from "mouse nests," this flea may be found to be a nest inhabiting parasite. Some fleas are possible bridges by which a blood parasite could be transmitted from one kind of a mammal to another. If _Ctenophthalmus pseudagyrtes_ acted as the intermediate host of a disease-causing organism, an epizootic from _Microtus ochrogaster_ might be transmitted to _Pitymys nemoralis_ or to _Sigmodon hispidus_ or _Blarina brevicauda_. There are several other such potential bridges for blood parasites. Although table 6 does not prove that individual fleas wander from one host to another, the frequency with which the several kinds of fleas are removed from live mice suggests that the fleas occasionally do so. LICE (ANOPLURA) Lice collected from the prairie vole were all of one species, _Hoplopleura acanthopus_ (Burmeister). Of 59 voles examined for the presence of lice, 33 were found to be parasitized; the 59 voles had an average of 3.4 lice each. Other mice which used the same runways as the prairie vole had their own species of Anoplura. The cotton rat was host to _Hoplopleura hirsuta_ Ferris, and the two species of _Peromyscus_ were parasitized by _Hoplopleura hesperomydis_ (Osborn). The writer collected _Hoplopleura acanthopus_ from _Microtus californicus_ at Calaveras Dam, Alameda County, California, and from _M. pennsylvanicus_ at Ithaca, Tompkins County, New York. Elton, Ford, Baker, and Gardner (1931) recorded this same species from _M. argestis_ in England. Lice on the prairie vole are the same species as those found on other species of _Microtus_ in other areas, but since Anoplura of the prairie vole do not parasitize the cotton rat, the white-footed mouse, and the deer mouse, this host specificity of lice makes it unlikely that lice would carry blood parasites from the prairie vole to any of the latter named rodents. MITES (ACARINA EXCEPT IXODOIDEA) Many of the small mammals examined in this study had mites, some of which were collected and identified. Mites were collected from other species of voles in several localities in the United States and in one locality in Canada; as voles in widely separated regions are sometimes hosts to the same species of mites, these records will be presented here. The frequency of some kinds of mites in the identified material suggests that they are more abundant than other kinds. The occurrence of mites on small mammals from Lawrence, Kansas, is presented in table 7.