Large Swarms of Insects that Resemble Mosquitoes in Marin and Sonoma Counties

Release date: 
Feb 28

Cotati, Ca - Marin and Sonoma counties are home to numerous insects that closely resemble mosquitoes. According to the Marin/Sonoma Mosquito and Vector Control District, many of these insects have begun to emerge in large numbers, causing the public great alarm. In some areas, these insects have been found covering the sides of homes, in breezeways, near front doors, and swarming over lawns and bike trails.

"These insects are quite easy to confuse with mosquitoes for a couple of reasons," stated John Walker, Field Supervisor for the Marin/Sonoma Mosquito and Vector Control District. "First, most people believe that mosquitoes swarm, when in actuality mosquitoes generally do not swarm, at least not in the giant clusters most people come in contact with this time of year; second, these insects actually do resemble mosquitoes," stated Walker.

Here are the two most commonly found insects that resemble mosquitoes in Marin and Sonoma counties:

NON-BITING MIDGES: Non-biting midges are small flies that look like mosquitoes. While these insects do not pose a health threat, they can be a serious nuisance, particularly in communities adjacent to large aquatic habitats. During peak emergence, massive swarms of these midges can cover houses, cars, and other structures. Homes and buildings with outside lighting will attract large numbers of non-biting midges.

FUNGUS GNATS: Fungus gnats are common in the fall, spring, and early summer. Female fungus gnats lay their eggs in moist organic material or potting soil. The larvae feed on fungus, preferring leaf litter and decaying vegetation.

The District does not control fungus gnats or non-biting midges. If you do find that you are being bitten, however, contact the District at 707-285-2200. It is possible that there may be standing water that is producing mosquitoes in your area.

For more information about the Marin/Sonoma Mosquito and Vector Control District's free programs and services visit