Female mosquitoes deposit eggs singly or in rafts on or near
standing water. These eggs are very small, and hatch within a few
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.
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 www.smcmvcd.org/help
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
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.
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.
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.