A. vivida ranges at least from Mexico to southern Alberta, and larvae live in both warm and cold streams. In warm (geothermally heated) sites in Alberta, Oregon and Idaho, the life cycle is generally univoltine and larval growth is regulated by a short-day induced diapause in the penultimate larval instar. In sites with naturally fluctuating temperature regimes, however, the life cycle appears to be generally semivoltine. The role of diapause in this 2-year life cycle is presently unknown.