
Culex mosquitoes
Culex tarsalis and Culex pipiens
Culex tarsalis is the most important West Nile virus vector in Colorado. It breeds in irrigation runoff, ditches, ponds, flooded fields and other sunlit standing water, and it feeds on birds as well as people, which is how the virus moves from birds to humans. The related northern house mosquito (Culex pipiens) breeds in catch basins, containers and polluted water. Culex mosquitoes bite mainly from dusk through dawn, and West Nile risk in Colorado usually peaks from late July through August.






