Mosquito feeding

There are approximately 3,000 species of mosquitoes in the world. Nearly 4 million people worldwide die each year from mosquito-borne diseases. In San Diego County, there are 27 different species of mosquitoes, at least 9 of which are known to carry diseases that can be passed to humans. Native Culex mosquitoes can transmit West Nile virus and tend to bite during dusk and dawn. Invasive Aedes mosquitoes bite during the day and can transmit Zika, dengue, yellow fever, and chikungunya viruses.

Mosquitoes have a long biting proboscis that the females use to drink blood. This proboscis one way to tell a mosquito apart from many harmless mosquito look-a-likes. Mosquitoes, unlike other pests like gnats, do not form swarms.

All mosquitoes lay their eggs in or near standing water. Finding and removing or treating standing water is the best way to control mosquito problems. 

The Mosquito Life Cycle

Mosquito life cycle

A mosquito has four stages of life:

1. Egg: Once laid in water, eggs will hatch in 2 to 3 days. Invasive Aedes eggs can survive over a year in dry containers, and hatch when water is added. 

2. Larva: A mosquito larva looks like a tiny wiggling worm in the water.

3. Pupa: A larva becomes a pupa and the adult mosquito develops inside. Mosquitoes can go from egg to adult in less than 1 week during periods of warm weather. 

4. Adult: Adult female mosquitoes bite and drink blood. The average mosquito will live for about 2 weeks.

buckets with standing water

Prevent Mosquito Breeding

Mosquitoes lay their eggs in standing water.  To prevent mosquito breeding, check for and dump out standing water inside and outside at least once a week, in places such as buckets, birdbaths, saucers under potted plants, and children's toys. 

Add mosquito fish (available free of charge from the
Vector Control Program) or a mosquito larvicide (available for purchase at home and garden stores, follow all instructions on the label) to water in backyard ponds, fountains, and unfiltered pools. 

Use our Prevention Checklist as a guide to get started!

Protect Against Bites

applying insect repellent
  • Put screens on windows and doors. Fine mesh screen can prevent mosquitoes from getting inside homes. Aedes mosquitoes can live and breed indoors.
  • Wear long sleeves and pants. They are aggressive biters indoors and outdoors, especially during the day.
  • Apply insect repellent containing an EPA approved active ingredient such as: DEET, picaridin, oil of lemon eucalyptus, Para-menthane-diol, 2-undecanone, or IR3535.  Use insect repellent as directed on the label. 
green pool


  • High levels of mosquito activity
  • Green pools or other mosquito breeding sources
  • Dead birds, such as crows, hawks, jays, and owls


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