To clarify the life cycle of a plagiorchiid species which uses Radix natalensis as a first intermediate host for its larval development in Egypt, this study was carried out to investigate subsequent invertebrates where xiphidiocercariae of this digenean might encyst. Laboratory-bred R. natalensis and Culiseta longiareolata larvae (mosquito) were experimentally exposed to xiphidiocercariae under laboratory conditions. At 24h post-exposure, 70% of exposed juvenile R. natalensis were found harboring encysted cercariae in their tissues. In addition, C. longiareolata larvae of each developmental stage were infected with these xiphidiocercariae. Compared to unexposed mosquito larvae, a significantly higher mortality rate in first- and second-stage (L1& L2) larvae was noted. Prevalence of infection was also significantly higher in these L1 & L2 (90% & 88%, respectively) than in third- and fourth-stage larvae. Mosquitoes emerging from exposed L1 & L2 were significantly less numerous when compared to corresponding control groups. Significant disturbance in male and female sex ratio was noted in L1- & L2-developing mosquitoes; it was equal in L1-emerging adults and slightly male biased for those coming from L2.