Mosquito Larval Collections from April 2020

Breeding sources of mosquito larvae are declining as spring progresses and many impounds and marsh sources are drying. Mosquito breeding shifts during warmer months primarily to backyard ornamental ponds, fountains and containers, and creeks with standing water pockets and underground sources like storm drains or leaking pipes. This April there were 74 larval samples submitted to the laboratory. The most frequently occurring species in larval samples was Culiseta incidens, the cool weather mosquito, present in 42 of the 74 larval samples. This mosquito is found year-round in a variety of sources, especially backyard fountains and fish ponds. It is not known to transmit diseases. Culex pipiens, the northern house mosquito, was also collected frequently this past month, although in only twelve of the 74 samples. This is the most common mosquito in San Mateo County and is found year-round.  It is present more abundantly than the number of samples indicates, because it is also in sources that are routinely treated without the collection of lab-identified larval samples, such as catch basins. Anopholes punctipennis, the woodland malaria mosquito, was detected in a larval sample for the first time this year. This summer mosquito breeds in natural sources, like freshwater pools and streams.