Abstract: Pupal and adult stages of A. sinensis could be infected with R. jingdeensis when 4th-Instar larvae were exposed to preparasites, and the ratio of nematodes in late 4th-instar carried into adult mosquitoes was much higher than that of nematodes in early 4th-instar. This was the first time that the mermithid parasite was found within the pupal and adult stages of anopheline mosquitoes. Another experiment showed that the nematodes arrested ovarian development in most females, only one female was found with completed ovarian development, so the possibility could not be excluded that the infected adults might serve as a vehicle to spread nematodes to other breeding sites. Infectedmosquitoes appeared to have mating activity because sperms were found in the sperma-theca of an infected adult female. The pupae were insusceptible to prepasraites when they were directly exposed to the nematode.