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

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 HERE.

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.

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.

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; however, 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.