Effect of air temperature and humidity on the survival of pre-imaginal stages of two flea species (Siphonaptera : pulicidae)

The survival of immature fleas at 25 and 28 degreesC and 40, 55, 75, and 92 % RH was studied to test the hypothesis that the difference in microclimati c preferences determines habitat distribution of Xenopsylla conformis Wagne r, 1903 and Xenopsylla ramesis Rothschild, 1904. Survival of X. conformis e ggs did not depend on either temperature or humidity or both, whereas eggs of X. ramesis survived significantly less at 40% RH than at higher humiditi es. No larva of either species survived at 40% RH at either temperature. La rval survival of both species at both temperature regimes was significantly lower at 55% humidity than at higher humidities. Maximal survival time of larvae that died before pupation depended on both temperature and humidity in both species. Change of humidity during early stages of the life cycle ( from egg to larva) increased the maximal survival time in X. conformis larv ae but decreased that in X. ramesis larvae. Pupil survival was higher at hi gher humidities independent of temperature. Survival of X. conformis pupae was lower than that of X. ramesis pupae when the relative humidity was low. Humidity change on later stages (from lama to cocoon) decreased X. conform is pupal survival and had no effect on X. ramesis pupal survival. The sex r atio of emerged adults was not affected by either temperature or humidity i n both species. Changes in humidity between egg and larval environments sig nificantly decreased the percentage of females in X. conformis emergence at 28 degreesC.