Much work has been done concerning those parasites found upon the host. Very little has been done concerning those parasites that are parasitic but are very rarely found upon the host. Therefore, the purpose of this study is to determine seasonal distribution of those fleas found in the nests of the desert wood rat (N. l. lepida). This paper shows that there is a seasonal variation of flea populations within a certain geographic area. It also shows that certain species of fleas are distributed seasonally; not all species being present in the same season. Three of the eleven species collected from the nests are plague implicated, being either potential or capable vectors. A number of other nest consortes were found to demonstrate seasonal variations to some extent. Collecting and laboratory methods for the collection and preparation of fleas are discussed.