Bug FAQWestern Treehole Mosquito
Aedes sierrensis · Order: Diptera · Family: Culicidae
Source: Wikipedia
The Western tree-hole mosquito (Aedes sierrensis) lives in western North America, especially in oak and mixed-deciduous forests from southern California up to British Columbia and east to Utah. It breeds in water-filled cavities of trees such as oak, laurel, madrone and eucalyptus, and the adult females bite humans and other large mammals, often causing a nuisance.
Source: Wikipedia
Does it bite or sting?
They are aggressive biters, most active outdoors in mid-morning and late afternoon, and they tend to avoid direct sunlight.
Source: Wikipedia
Where it lives
It is found in oak and mixed deciduous forests across western North America, from southern California to British Columbia and east to Utah. The mosquito prefers breeding in water-filled tree cavities, especially in oak, laurel, madrone and eucalyptus.
Source: Wikipedia
What it eats
Adult females feed on the blood of humans and other large mammals.
Source: Wikipedia
Life cycle
The species usually has one generation per year. Adults emerge from overwintering larvae in spring, with numbers peaking in April and May.
Source: Wikipedia
When you see it
They are most active from March through August.
Source: Wikipedia
Where it comes from
Aedes sierrensis is native to western North America.
Source: Wikipedia
Where it is found in the US
Recorded in 6 of 51 states and DC. Most records: California, Washington, Montana, Utah, Idaho, Oregon.
Darker = more records. Counts are museum and citizen-science records, not population size.
Source: GBIF
Status: native in North America; native in Canada. Source: iNaturalist
Months it is reported in the US
Source: GBIF
More photos
Questions people ask
Do they bite?
Yes, the adult females bite humans and other large mammals, often causing a nuisance.
Source: Wikipedia
Where do they live?
They live in oak and mixed-deciduous forests of western North America, from southern California to British Columbia and east to Utah.
Source: Wikipedia
When are they most active?
They are most active from March through August, especially in mid-morning and late afternoon.
Source: Wikipedia
How many generations do they have each year?
The species typically produces one generation per year.
Source: Wikipedia
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/Aedes_sierrensis
Look it up elsewhere: GBIF · iNaturalist · BugGuide · ITIS · Wikipedia
Text written 2026-10-23 from the sources above and checked sentence by sentence against them. Data fetched 2026-10-23.