Two invasive (non-native) mosquito species have been found throughout California. They are named Aedes aegypti (the yellow fever mosquito) and Aedes albopictus (the Asian tiger mosquito). Unlike most native mosquito species, Aedes aegypti and Aedes albopictus bite during the day. Both species are small, black mosquitoes with white stripes on their back and on their legs. They are known as “container breeders” and can lay eggs in any small, artificial, or natural container that holds water, even as small as a bottle cap! These eggs can withstand being dried out for over a year before water is reintroduced and the eggs can hatch. If you suspect you might have invasive Aedes in your neighborhood, please submit a Service Request for assistance.
Aedes aegypti larvae in a bottle cap. Credit: CDC
The adults are small and black with many white markings on their body. They originate from tropical and subtropical regions of the world where they have evolved alongside humans and developed many unique traits. Local mosquito species are mostly attracted to birds and other large mammals, with humans being incidental targets. Aedes aegypti and albopictus females on the other hand, specifically target humans for their blood meals and are known to bite at the ankles and elbows where humans have less nerve endings and thus less likely to feel a bite. They have also been shown to take smaller blood meals from multiple hosts which increases the likelihood of spreading mosquito-borne diseases between people.
Aedes aegypti, notice the distinct “lyre” shape on the top of the thorax. Credit: California Dept. Public Health
Unlike our native mosquitoes that are active at dusk and dawn (known as being crepuscular) invasive Aedes are day-time biting mosquitoes that often swarm, unlike most native species in our county.
Aedes aegypti and Aedes albopictus have the potential to transmit several viruses, including dengue, chikungunya, Zika, and yellow fever. In the summer of 2023, Southern Californian cities reported local transmission of dengue fever for the first time. This means that the people who became sick did not have any recent travel to areas where the disease is prevalent but instead were bitten and infected by the invasive Aedes mosquitoes in their own neighborhood.
When an invasive aedes mosquito is detected, all the yards of homes in the neighborhood and adjacent areas need to be very thoroughly inspected to ensure there are no nearby breeding sources. This can be difficult and time consuming for both the homeowners and the mosquito control technicians. Without full cooperation from the affected neighborhoods, invasive Aedes mosquitoes can thrive and multiply from just a few breeding sources.
In October 2022, we had our first invasive Aedes detection in Watsonville, California. This initiated a large trapping and inspection effort in the neighborhood that continued into the two next years.
When an invasive aedes mosquito is detected, all the yards of homes in the neighborhood and adjacent areas need to be very thoroughly inspected due to how small and hidden invasive Aedes breeding habitat can be. This can be very difficult and time consuming for both the homeowners and the mosquito control technicians. Without full cooperation from the affected neighborhoods, invasive Aedes mosquitoes can thrive and multiply from just a few breeding sources. Unlike most of our native species, invasive aedes do not fly far from their breeding sites. If you collect rainwater, make sure your rain barrel remains securely screened/sealed to stop mosquito breeding and check and dump containers that hold water around your home often. If you suspect you might have invasive Aedes in your neighborhood, please submit a Service Request for assistance.