Invasive Species

Since 2011, two mosquito species not native to California have been detected in an increasing number of cities across the state, from the sprawling urban areas of San Diego and Los Angeles counties, through small suburban communities in the central valley, and up to San Mateo County in the San Francisco Bay Area. Their potential for creating day-time biting nuisance and transmitting life-threatening or debilitating diseases is cause for serious concern.

Although we have not found these mosquitoes in Placer County yet, we need your help to detect them as early as possible.

Aedes aegypti (the yellow fever mosquito) is an efficient carrier of dengue, yellow fever, chikungunya, and Zika viruses, none of which are currently known to be circulating in the state. Aedes aegypti is a small, dark-colored mosquito, recognized by its distinctive white markings and banded legs. It may be most active at dusk but can be an aggressive day biter and readily enters homes for shelter and to feed on people.


Aedes albopictus (the Asian tiger mosquito) also has the potential to transmit dengue and chikungunya viruses. This daytime biting mosquito is characterized by its small size and black and white stripes across its body and legs.


Some common characteristics of these new species:

  • These mosquitoes are aggressive people-biters that are most active during the day both indoors and outdoors.
  • The entire life cycle, from egg to adult, can occur in as little as 7-9 days. The life span for adult mosquitoes is around three weeks.
  • They have a short flight range, so mosquitoes are usually found in the same general area of the water source where they hatched as eggs.
  • Eggs are laid over a period of several days, are resistant to drying out, and can survive for periods of six or more months. These mosquitoes remain alive through the winter in the egg stage and when the eggs are covered with water in warm weather, the larvae hatch.
  • They use artificial and/or natural habitats to lay their eggs.

Below is a map of where the species have been detected:


Click this link to view, download or print an informational sheet on how to prevent these mosquitoes from making themselves at home in your backyard: Invasive Species Information Sheet

For more information about invasive species in California, please visit the California Department of Public Health website Invasive Aedes page.

For more information about Zika virus, please visit the California Department of Public Health Zika webpage.