Some aspects of overwintering in southern England of the mosquitoes Anopheles atroparvus and Culiseta annulata (Diptera: Culicidae)

. 1. Overwintering of the mosquitoes Anopheles atroparvus van Thiel and Culiseta annulata Schrank, both of which feed on blood throughout the year, is compared. 2 The aquatic stages, males and gonoactive females of A.atroparvus disappear before winter, leaving a generation of inseminated, nulliparous, diapausing females to overwinter. Blood meals taken by diapausing females merely serve to maintain fat reserves. After re-activation in March–April, gonoactive life expectancy appears to be rather short. Aquatic development at this season is slow and eggs laid in the spring do not significantly affect adult densities until June. 3. Aquatic stages, males and gonoactive females of C.annulata are present throughout the year. This species appears to be able to overwinter without recourse to diapause, females passing the winter in alternating, or lasting, states of cold-induced quiescence or normal gonoactivity.