Marin/Sonoma Mosquito & Vector Control District
800-231-3236 (toll free)
707-285-2200 (office)
595 Helman Lane, Cotati, CA 94931-9736

PHONE
800-231-3236 (toll free)
707-285-2200 (office)
707-285-2210 (fax)

ADDRESS
595 Helman Lane
Cotati, California
94931-9736

HOURS
Monday through Friday
7:00AM to 3:30PM

1. THE SALT MARSH MOSQUITO (OCHLEROTATUS SQUAMIGER)

Twenty four Ochlerotatus species make up the largest mosquito genus in California. Adult females have short palpi and a pointed tip on the abdomen, but there is no single distinguishing feature that separates all Ochlerotatus from other mosquitoes. Most produce only one generation each year. In the spring, they lay their batches of eggs singly along at the edges of drying pools of water. The eggs require a period of rest before development can proceed after the pools refill in the winter.

The salt marsh mosquito, Ochlerotatus squamiger, has rings of white scales around each segment of the hind legs and abdomen. The wings are speckled with dark and light scales. It makes up the first spring wave of salt marsh mosquitoes, and develops especially high numbers in the lower Petaluma and Sonoma basins. A strong flyer, it easily reaches nearby cities during its early morning and late afternoon flights.

This is a significant pest mosquito, inhabiting coastal regions from Sonoma County south to Baja California. Its extreme nuisance around Burlingame in the southern part of the San Francisco Bay attracted the attention of entomologists from the University of California, and resulted in the state's first definitive scientific report on California mosquitoes, published in 1906.

Biologists have estimated that up to four million Ochlerotatus squamiger can be produced in one acre of salt marsh. Vector technicians with the Marin / Sonoma Mosquito and Vector Control District have trapped more than 10,000 adults in one Fay trap operating over a single night in Novato.

Photo: Fay trap

Ochlerotatus squamiger breeds in brackish intertidal waters and drainage ditches. Eggs are laid just above the high tide mark as water levels recede in the late spring. They remain dormant through the summer, and hatch during the winter and early spring when rain and high tides once again flood the marshes. The larvae develop slowly and adults emerge 40-50 days later. Adults migrate into nearby forested areas, and then return in the spring to lay their eggs.