Selected mosquito vectors of West Nile virus: comparison of their ecological dynamics in four woodland and marsh habitats in Delaware.

We compared human landing, CO2-baited light trap, CO2-baited Omni-Fay trap, and gravid trap collections of mosquitoes at 4 woodland and marsh sites with varied vegetative habitats in Delaware during summer 2001. Landing collections provided more consistent, but sometimes smaller, collection numbers than light traps. Proportions of parous mosquitoes were also higher in landing than in light trap or Omni-Fay collections about 65% of the time. Circadian feeding rhythms were observed for 3 suspected vector species selected on the basis of 1999-2000 laboratory vector competence data and their presence at local habitats. These species included Aedes vexans, Culex salinarius, and Cx. pipiens pipiens. Aedes vexans fed after dusk, primarily before 2200 h and again around dawn (0600-0700 h). Both Cx. salinarius and Cx. p. pipiens exhibited peak feeding activity after dusk and in predawn periods, as well as extended feeding periods up until midnight. Time of feeding is an important factor in evaluating vector-host associations and risks of human outbreaks.