Mosquito bionomics and the lack of arbovirus activity in the Chino area of San Bernardino County, California.

Mosquito bionomics, including temporal abundance, metabolic status, and blood-feeding patterns, and arbovirus activity were studied at representative dairy and residential habitats in Chino, Calif., during 1987 and 1988. Host-seeking Culex tarsalis Coquillett and Cx. quinquefasciatus Say females were more abundant and appeared earlier each season at traps near dairy breeding sources than at traps in residential areas, whereas Cx. stigmatosoma Dyar, which also breeds in dairy effluent, was most abundant at residential traps. All three Culex species remained gonotrophically active throughout winter and did not appear to enter diapause. Dairy cows diverted the normally ornithophagic Cx. tarsalis and Cx. quinquefasciatus females from avian hosts in dairy, but not in residential, habitats. Cx. stigmatosoma fed almost exclusively on birds. The diversion of host-seeking Cx. tarsalis females to bovine hosts and reduced abundance because of mosquito abatement may have combined to reduce the receptivity of the Chino area to St. Louis encephalitis virus.