On the Relationships of Some Mammal Fleas to Their Hosts

Knowledge of the biology of fleas in their native environments consists chiefly of records of their geographical and host distribution. Information about their life histories and host relationships is limited very largely to that acquired in epidemiological investigations of plague and of other flea-borne diseases. Such work has usually been governed by hygienic and economic necessity and unfortunately has not always been endowed with a broad ecological point of view. Considerable attention has been given to the development of a “satisfactory” flea index, that is, an estimate of the density of flea populations as indicated by samples taken from the hosts, whereas little has yet been done to elucidate the factors which determine the density of the population-at-large, of which the individuals collected on hosts may be a small and varying fraction. The paucity of material on the ecology of fleas has prompted us to prepare these somewhat fragmentary notes.