Bug FAQBlunt Knapweed Flower Weevil
Larinus obtusus · Order: Coleoptera · Family: Curculionidae
Also called: Knapweed Seedhead Weevil, Weevil
The blunt knapweed flower weevil is a small dark-brown beetle with a large bulbous snout, measuring about 5 to 7 mm long. Adults lay yellow eggs in open knapweed flower heads in summer; larvae develop inside the seed head for about 17 days, pupate in a seed-remnant cocoon for roughly nine days, and adults live 58 to 94 days.
Source: Wikipedia
How to recognize it
Adults are dark brown and have a large, bulbous snout.
Source: Wikipedia
Size
They are 5 to 7 mm long (about 0.19 to 0.27 inches).
Source: Wikipedia
Where it lives
They are active throughout the summer when females lay yellow eggs in opened flower heads.
Source: Wikipedia
What it eats
Larvae emerge and feed on the developing seeds inside the knapweed head. Adults feed on foliage but cause only minor damage to the plant.
Source: Wikipedia
Life cycle
The larval stage lasts about 17 days, after which the larva builds a cocoon from seed remnants and pupates for roughly nine days. Males live on average about 94 days and females about 58 days.
Source: Wikipedia
When you see it
They are active throughout the summer.
Source: Wikipedia
Lookalikes
It resembles its relative Larinus minutus, another knapweed specialist used for biocontrol.
Source: Wikipedia
Where it is found in the US
Recorded in 26 of 51 states and DC. Most records: Michigan, New York, Massachusetts, Wisconsin, Vermont, Colorado, Oregon, Pennsylvania.
Darker = more records. Counts are museum and citizen-science records, not population size.
Source: GBIF
Status: introduced in Canada. Source: iNaturalist
Months it is reported in the US
Source: GBIF
More photos
Questions people ask
What does the adult blunt knapweed flower weevil look like?
Adults are dark brown with a large, bulbous snout.
Source: Wikipedia
When are these weevils active?
They are active throughout the summer, laying eggs in open flower heads.
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/Larinus_obtusus
Look it up elsewhere: GBIF · iNaturalist · BugGuide · Wikipedia
Text written 2026-10-24 from the sources above and checked sentence by sentence against them. Data fetched 2026-10-24.