Mosquito larvae collections from August 2020

During August, larval surveillance focused on backyard sources like fountains, ponds, and containers in addition to catch basins. A technician uses a dipper to take a sample of the water and visually inspects it for mosquito larvae. If larvae are present, the technician transports the sample to the laboratory for counts and identification. This August, 63 larval samples were submitted to the laboratory. The most frequently occurring species in larval samples was Culiseta incidens, the cool weather mosquito, present in 33 of the 63 samples. This mosquito is present year-round in San Mateo County and frequently collected from backyard sources such as fish ponds, containers holding water, and fresh water impounds. Culex pipiens, the northern house mosquito, was also collected frequently this past month. Culex pipiens is the species most commonly associated with biting complaints in San Mateo County. It breeds in organically enriched water from a variety of sources, such as catch basins, unmaintained swimming pools, and leaks under buildings. Several larval samples also had specimens of Aedes dorsalis, the summer salt marsh mosquito. Aedes dorsalis is commonly collected in pockets of water in the marshes along the San Francisco Bay from Foster City to East Palo Alto in the summer months.