Winter Survival of Culex Tarsalis (Diptera: Culicidae) Hibernating in Mine Tunnels in Boulder County, Colorado, USA

The mark-release-recapture technique was applied to the study of winter survival among hibernating Culex tarsalis for the first time. Three hundred and seventy-seven hibernating Cx. tarsalis females were collected from an abandoned gold mine tunnel near Jamestown, Colorado, on 19 October 1977, marked with a zinc sulfide dust, and released into the mine. Recovery of 8.7% of the marked population 3 to 5 months later provided only a crude estimate of survival rates; however, this study represents the first attempt to quantify survival rates among an unrestrained overwintering population of Cx. tarsalis. A total of 1088 female Cx. tarsalis were collected from this and surrounding mines from September 1977 through March 1978. The parity status of 606 specimens was 2.8% parous, 89.9% nulliparous, and 7.3% undetermined. A total of 905 Cx. tarsalis collected from September through March was tested for arboviruses, generally after being kept alive in the laboratory for 2 weeks at 26.7 °C and a 16-h photophase and after having fed on a chick, but no virus was isolated from either the mosquitoes or the chicks.