We monitored eclosion patterns of adult Coquillettidia perturbons (Walker) in the Minneapolis – St. Paul region of Minnesota directly using emergence traps (1983, 1984, and 1992), and indirectly using CO2-baited adult traps (1987–1992) and larval sampling (1988 and 1989). Most mosquitoes eclosed in a unimodal pulse during June although peak eclosion periods varied among years and sites. It required 26.6 ± 1.5 days for 90% of individual populations to eclose. Temporal abundances of host-seeking females also suggested unimodal eclosion with peaks typically occurring in June and July. Most larvae overwintered in the fourth instar and pupated in early summer, as expected from adult data. However, many larvae overwintered in the third instar and did not molt into the fourth until July, which was after most eclosion was completed. These individuals may eclose in autumn or may spend a second winter as larvae.