Mosquito Identification & Info


Identification & Info

Mosquito larvae congregate near the surface of still water.
The mosquito life cycle.

The Mosquito Life Cycle


Female mosquitoes deposit eggs singly or in rafts on or near standing water. These eggs are very small, and hatch within a few days.


Mosquito larvae emerge from mosquito eggs. They float near the water surface where they can breathe, but may move in a wriggling motion when disturbed. Mosquito larvae feed on microorganisms and other debris in water.


Invasive Mosquitoes

If you believe you have seen invasive Aedes mosquitoes in San Mateo County, please call (650) 344-8592 or make a service request for insect identification at

Aedes aegypti (Yellow Fever Mosquito)

Native to Africa, but found in many tropical and subtropical regions worldwide. Bites humans during the day. Capable of transmitting yellow fever, dengue fever, and chickunguna viruses (the risk of these viruses is low in San Mateo County).


Common Mosquitoes

Culex pipiens (Northern House Mosquito)

Present year-round. Breeds in foul or polluted water. Feeds on birds and mammals, including humans. Readily enters buildings and bites indoors. Can transmit West Nile virus, Western Equine Encephalitis, and St. Louis Encephalitis.


Seasonal Mosquitoes

Aedes squamiger (California Salt Marsh Mosquito)

Adults emerge in March and remain active through June. Breeds in coastal salt marshes but may fly up to 20 miles. Bites aggressively during the day. May become a major pest to humans.

Aedes dorsalis (Summer Salt Marsh Mosquito)

Adults are active late spring into the fall. Breeds in tidal or reclaimed marshes, but may fly long distances. Aggressively bites during the day. Can be a major pest to humans and a secondary vector for Western Equine Encephalitis.


Less Common Mosquitoes

Culex stigmatosoma (Banded Foul Water Mosquito)

Adult activity peaks in the summer months. Breeds in natural and man made polluted waters. Feeds primarily on birds but may rarely bite humans. May transmit St. Louis Encephalitis.

Coquillettidia perturbans

Adults are active in June and July. Breeds in fresh water with cattails and tules. Feeds on large mammals, including humans, after sunset. Transmits encephalitis viruses.


Other Mosquito-Like Insects

There are many flying insects that look similar to mosquitoes and may be mistaken for mosquitoes. These insects can be annoying at certain times of year but unlike mosquitoes, they do not bite and cannot transmit disease. The District does not usually control these insects because they are not a threat to public health.