The life history of Cricotopus myriophylli Oliver is described from both field observations and laboratory rearing of field-collected larvae. The species appears to be univoltine with four larval instars and has a sex ratio of ca. 2:1, males to females. Emergence begins in late May in British Columbia and continues until mid-September, with first-instar larvae present in the field from mid-June to mid-August. Water temperature does not appear to influence the rate of emergence. In the laboratory at 21 °C, larvae complete each of the third and fourth instars in 10–14 days. Cricotopus myriophylli overwinters primarily in the third larval instar, although second and fourth instars were also recovered in field-collected samples. First-instar larvae and eggs were not recovered from winter samples. This species does not appear to undergo a true diapause.