City Lights Are Lengthening The North American Mosquito Season

InnovationScienceCity Lights Are Lengthening The North American Mosquito SeasonByJohn Drake,Contributor.Forbes contributors publish independent expert analyses and insights. John Drake is a professor at the University of Georgia. Follow AuthorMay 28, 2026, 06:00am EDT--:-- / --:--This voice experience is generated by AI. Learn more.This voice experience is generated by AI. Learn more.The common house mosquito, Culex pipiens (Photo by Herbert SCHWIND/Gamma-Rapho via Getty Images)Gamma-Rapho via Getty ImagesArtificial light at night is among the most pervasive forms of environmental change on Earth. More than 80 percent of the human population now lives under light-polluted skies, and that figure grows by a few percent each year. Research over the past decade has documented disruptions to the biology of birds, insects, bats, sea turtles and flowering plants, most of them traceable to artificial light that is scrambling the circadian and photoperiodic systems that organisms use to coordinate their behavior, physiology and timing with the rest of the natural world.A new study in the Journal of Applied Ecology asks what city lights do to the autumn dormancy of the northern house mosquito, Culex pipiens, the primary vector of West Nile virus in cities across the northeastern and midwestern United States. The answer is that dim residential lighting, at intensities typical of a porch light, suppresses mosquito dormancy more powerfully than even urban warming does. Mosquitoes that should be sleeping in October are still biting, still blood-feeding, still producing eggs.The Dormancy SignalEach autumn, as day length shortens, female Culex pipiens enter diapause: a state of developmental arrest in which they stop seeking hosts, halt egg development, accumulate fat reserves, and seek sheltered hibernation sites. While dormant, they cannot transmit pathogens. The predictable decline of West Nile virus cases in October across the northern United States reflects this shutdown.The s...