Mosquito Trapping

Mosquito Trapping:

Carbon Dioxide Mosquito Trap

The District has an extensive mosquito trapping program. This information is used to direct control efforts and to detect diseases. Carbon dioxide traps are set up throughout the county to collect mosquitoes. A trap consists of a thermos filled with dry ice, connected to a fan, run on batteries, covered by a net bag. Mosquitoes are attracted to carbon dioxide given off by the dry ice as it melts, which mimics human breathing. As mosquitoes come close to the thermos, they are sucked down by the fan and into the net bag. A portion of collected mosquitoes are used in disease surveillance to test for West Nile virus and other mosquito-borne diseases.

The graph below details the population of the five most commonly encountered mosquitoes found in San Mateo County: Ae. sierrensis, Ae. squamiger, Ae. washinoi, Cx. pipiens, and Cx. erythrothorax. Population densities are estimated based on the number of female mosquitoes collected in a given 24-hour period. They are tallied and averaged over five years, by month, to account for changes in population due to environmental and sampling factors.