SUMMARY.The life cycle ofTrichocorixa verticalis interioreswas studied in six Saskatchewan saline lakes. A detailed study of the timing of the stages in the life cycle showed thatT. v. interioreshas a life cycle which differs from that of all other Corixidae. This species overwinters solely in the egg stage. Females oviposit in the late summer and all adults die in the fall. The eggs, which remain in a pre‐blastokinesis stage of embryonic development until the following spring, are prevented from developing in late summer by diapause which lasts approximately 2 months. Although diapause terminates in October, embryonic development does not occur in cold water during the winter months. Experimental results indicate that exposure to cold is not necessary to break diapaus