Bug FAQWestern Encephalitis Mosquito
Culex tarsalis · Order: Diptera · Family: Culicidae
Western Encephalitis Mosquito (Culex tarsalis) is found across North America and is known for its black-and-white leg bands. Females need blood meals and can spread Saint Louis, Western equine, and West Nile encephalitis viruses. Eliminate standing water and use fish or bacterial larvicides to keep their numbers down.
How to recognize it
Adults have distinctive black and white stripes on their legs. A photo credit shows the typical appearance of Culex tarsalis.
Is it a pest in the house?
Female mosquitoes require blood from humans, pets, livestock, or wildlife.
Source: UC IPM
Does it bite or sting?
Females bite to obtain blood and can transmit several encephalitis viruses.
How to get rid of it
Remove any standing water to reduce breeding sites. In ponds, trim excess plants, add mosquito-eating fish, or apply Bacillus thuringiensis products.
Source: UC IPM
What it eats
In addition to feeding on blood, they can carry avian malaria parasites that affect wild birds.
Source: Wikipedia
Where it comes from
The species occurs throughout North America.
Source: Wikipedia
Lookalikes
Non-biting midges and crane flies are often mistaken for mosquitoes, but they lack the long, slender proboscis used for biting.
Source: UC IPM
Where it is found in the US
Recorded in 33 of 51 states and DC. Most records: Iowa, North Dakota, Idaho, California, Utah, Montana, Nevada, Texas.
Darker = more records. Counts are museum and citizen-science records, not population size.
Source: GBIF
Status: native in North America; native in Canada; native in United States. Source: iNaturalist
Months it is reported in the US
Source: GBIF
More photos
Questions people ask
Do Western Encephalitis Mosquitoes bite?
Yes, female Culex tarsalis bite to obtain blood from people or animals.
Source: UC IPM
Can they spread disease?
They are confirmed vectors of Saint Louis, Western equine, and West Nile encephalitis viruses.
How can I control them around my home?
Eliminate standing water and treat ponds with fish or bacterial larvicides.
Source: UC IPM
Same family (Culicidae)
Asian Tiger MosquitoAedes albopictusCan spread germs or disease
House Mosquito ComplexCulex pipiensCan spread germs or disease
Yellow Fever MosquitoAedes aegyptiCan spread germs or disease
Inland Floodwater MosquitoAedes vexansCan spread germs or disease
Asian Bush MosquitoAedes japonicusCan bite
Southern House MosquitoCulex quinquefasciatusCan spread germs or diseaseSources
- Wikipedia: https://en.wikipedia.org/wiki/Culex_tarsalis
- UC IPM: https://ipm.ucanr.edu/PMG/PESTNOTES/pn7451.html
Look it up elsewhere: GBIF · iNaturalist · BugGuide · ITIS · Wikipedia
Text written 2026-10-22 from the sources above and checked sentence by sentence against them. Data fetched 2026-10-22.