The phenology of fourChaoborusspecies in four bog lakes in the upper peninsula of Michigan was documented. The sequence timing of pupation was:Chaoborus americanus, early May;C. flavicans, end of May;C. punctipennis, early July;C. trivittatus, end of August and early September.C. americanus,C. punctipennis, andC. trivittatuseach occurred in two of the lakes. Differences in the timing of pupation for each of these species between lakes were not always correlated with environmental differences between lakes.C. punctipennis,C. flavicans, and one of theC. americanuspopulations was univoltine. The otherC. americanuspopulation may have been bivoltine. OneC. trivittatuspopulation appeared to be univoltine, whereas the other may have had a 2-year generation time. The significance of the sequence and timing of pupation of these species is discussed in relation to seasonality, interspecific competition, and predation.