The following table and graph show the average number of mosquitoes collected per CO2 trap per night during the month of December compared to the five-year average for the six most common mosquito species in San Mateo County. Counts for all species are averaging below five per trap night, which is consistent with the five-year average. The numbers are expected to remain low until spring.
This table shows the number of acres treated with larvicide during November and December. The number of acres treated during these months is low. Technicians are currently monitoring sources for mosquito larvae as they fill with water. The mosquito larvae are treated with larvicide when they reach the optimal growth stage. The number of acres treated will likely increase substantially in January, especially in marshes and impounds, depending on rainfall.
Surveillance of water for mosquito larvae increases after autumn rainfall, when marshes, impounds and natural ponds fill with water. 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 December, 41 larval samples were submitted to the laboratory. The most frequently occurring species in larval samples was Cs. incidens, from 21 out of 41 samples.