Bug FAQCalifornia Acorn Weevil
Curculio occidentis · Order: Coleoptera · Family: Curculionidae
Source: Wikipedia
Curculio occidentis, called the filbert weevil, is a weevil species that lives on the western side of North America. Females lay two-to-four eggs inside developing acorns, and the larvae feed on the kernel, sometimes taking one or two years before pupating. Because the larvae eat the seed inside oak acorns, infested nuts still sprout but at a lower success rate, making the weevil a pest of oak trees.
Source: Wikipedia
Is it a pest in the house?
The weevil is considered a pest of many oak species because it damages acorns. Infested acorns can still germinate, but their germination rate is lower than that of healthy nuts.
Source: Wikipedia
What it eats
The larvae feed on the kernel of oak acorns, and together with the filbertworm moth they consume acorns of several oak species.
Source: Wikipedia
Life cycle
Females lay small batches of two to four eggs inside a developing acorn. The larvae may remain inside the acorn for one or two years before they pupate.
Source: Wikipedia
Where it comes from
Its range includes British Columbia, California, Arizona, New Mexico, Utah, and parts of Mexico.
Source: Wikipedia
Lookalikes
Its larvae are often found alongside those of the filbertworm moth, which also feed on oak acorns.
Source: Wikipedia
Where it is found in the US
Recorded in 7 of 51 states and DC. Most records: California, Oregon, Illinois, Massachusetts, Arizona, South Carolina, Texas.
Darker = more records. Counts are museum and citizen-science records, not population size.
Source: GBIF
Months it is reported in the US
Source: GBIF
More photos
Questions people ask
How does the filbert weevil damage oak trees?
Its larvae eat the seed inside oak acorns, reducing the nuts' ability to sprout.
Source: Wikipedia
Where is the filbert weevil found?
It lives on the western side of North America, from British Columbia down through several western U.S. states into Mexico.
Source: Wikipedia
What does the filbert weevil eat?
The larvae feed on the kernels of oak acorns, often sharing the food source with the filbertworm moth.
Source: Wikipedia
Same family (Curculionidae)
Green Immigrant Leaf WeevilPolydrusus formosusDamages trees, gardens or crops
Black Vine WeevilOtiorhynchus sulcatusDamages trees, gardens or crops
Nettle weevilPhyllobius pomaceusDamages trees, gardens or crops
Asian Oak WeevilCyrtepistomus castaneusDamages trees, gardens or crops
Strawberry Root WeevilOtiorhynchus ovatusDamages trees, gardens or crops
Common Leaf WeevilPhyllobius pyriDamages trees, gardens or cropsSources
- Wikipedia: https://en.wikipedia.org/wiki/Curculio_occidentis
Look it up elsewhere: GBIF · iNaturalist · BugGuide · Wikipedia
Text written 2026-10-29 from the sources above and checked sentence by sentence against them. Data fetched 2026-10-29.