The Transmission of Crithidia fasciculata Leger 1902 in Culiseta incidens (Thomson)*

SYNOPSIS. It has been shown that larva‐to‐larva transmission effected by means of free‐living Crithidia can account for the incidence of this flagellate in natural populations of adult mosquitoes. Larval infections lost at molting were reacquired early in subsequent instars. Infections of pupae came about by contamination of the midgut of the prepupa with nectomonads while the peritrophic membrane was being shed prior to pupation. By the time pupation was completed the flagellates had become immotile and continued to multiply in the pupal midgut; they again became motile in the midgut of the newly emerged adult. Adult‐to‐larva transmission was effected through water contaminated by adult mosquitoes infected with flagellates.