Mosquitoes are small, blood-feeding flies (Order: Diptera, Family: Culicidae). Most species are only 1/8 - 1/4” long. Adult mosquitoes have two wings and a long needle-like mouth (called a proboscis). Immature stages of mosquitoes are aquatic and do not resemble the adults. Mosquito larvae are elongated and often have a long respiratory siphon, while pupae are comma-shaped and have two smaller breathing tubes.   

Life cycle & habitat: 

Mosquitoes develop in a wide range of aquatic habitats; please view our Mosquito Production Sources Gallery to see a variety of places where mosquitoes commonly lay their eggs. Some species of mosquitoes lay large numbers of eggs directly onto standing water, while others deposit eggs in areas that periodically flood. Mosquitoes progress through four life stages: egg, larva, pupa and adult. Aquatic mosquito larvae hatch from eggs and develop into pupae. The pupae emerge from the water as adults. Warm temperatures generally encourage faster development, with some mosquitoes developing from egg to adult in approximately one week. Please see our Mosquito Life Cycle Gallery to see pictures of all life stages of mosquitoes. 

Impact on human health: 
  • Adult female mosquitoes may bite humans or other vertebrates (including pets, livestock and wildlife) to obtain the blood required for egg development.
  • Bites cause skin irritation and may become infected especially if the bite is scratched.
  • Worldwide, mosquitoes are known to transmit a wide range of pathogens, including virusesfilarial nematodes, and protozoans such as the parasite that causes malaria.
  • Locally, mosquitoes are known to transmit West Nile virus (WNV) to humans and dog heartworm to certain animals.
  • Click here for an overview of the District’s mosquito control activities.
What you can do to prevent exposure: 

Reduce outdoor exposure to mosquitoes:

  • Avoid being outdoors during peak mosquito activity (dawn and dusk).
  • Use mosquito repellents containing DEET, picaridin or oil of lemon eucalyptus (always carefully read and follow the directions on the label!)
  • Wear protective clothing.

Reduce indoor exposure to mosquitoes:

  • Keep doors and windows closed whenever possible.
  • Check and maintain all window and door screens.

Prevent mosquitoes from growing near your home:

  • Use this checklist to help identify areas around your home that may produce mosquitoes.
  • Flip, dump or drain all temporary sources of standing water.
  • Contact the Marin/Sonoma Mosquito & Vector Control District (800.231.3236) if you have a mosquito-related problem that you cannot resolve on your own.

Bohart, R.M. and R.K. Washino. 1978. Mosquitoes of California, 3rd ed. Division of Agricultural Sciences. Berkeley, CA.

Mullen. G.R. and L.A. Durden. 2009. Medical and Veterinary Entomology, 2nd ed. Academic Press. Burlington, MA.

Walton, W.M. and B.F. Eldridge. 2009. Pest Notes: Mosquitoes. Davis: Univ. Calif. Agric. Nat. Res. Publ. 7451.