Fleas Xenopsylla conformis mycerini and Xenopsylla ramesis replace each other on the same rodent host (Meriones crassus) in two habitats that differ in substrate texture (sand and loess-like sediments, respectively). We hypothesized that the substrate is an important factor determining flea distribution and studied survival of larvae, pupae and newly emerged adults as well as the rate of pre-imaginal development of these flea species in sand and loess rearing medium (= substrate). Texture of rearing medium did not affect survival and development rate of eggs in either X. c. mycerini or X. ramesis. Larval survival and the rate of development were both affected by the factor of substrate. Survival of X. c. mycerini larvae was significantly higher in sand than in loess substrate, whereas survival of X. ramesis larvae did not differ in different substrates. Larvae of both species developed faster in sand substrate than in loess substrate. Maximal survival time of X. c. mycerini larvae that died before pupation did not depend on substrate, whereas X. ramesis larvae survived significantly longer in loess than in sand substrate. Most pupae of both species survived successfully on both substrates, but the duration of pupal stages in sand substrate was longer than that in loess substrate in both species. Newly emerged adults of both species survived similar time in both sand and loess substrate. Irrespective of substrate, adult X. c. mycerini survived for a shorter time than did adult X. ramesis. No between-sex within-species differences in survival time of newly emerged adults in sand versus loess substrate were found in X. c. mycerini. Survival time of males and females of X. ramesis differed in sand substrate but not in loess substrate.