Bug FAQWillow Leaf Beetle (Chrysomela aeneicollis)
Chrysomela aeneicollis · Order: Coleoptera · Family: Chrysomelidae
The willow leaf beetle (Chrysomela aeneicollis) is a leaf-beetle in the family Chrysomelidae. It lives in cooler coastal areas from northern California up to British Columbia and at high elevations in the Rockies and Sierra Nevada. Adults emerge in early summer, mate, lay eggs, and produce one generation of larvae before winter dormancy.
Source: Wikipedia
How to recognize it
Chrysomela aeneicollis belongs to the leaf-beetle family Chrysomelidae.
Source: Wikipedia
Where it lives
Populations are found in cool coastal habitats from northern California to British Columbia and at high elevations in the Rocky and Sierra Nevada mountains.
Source: Wikipedia
What it eats
Larvae extract chemicals from the leaves they eat to make a defensive spray when threatened. Researchers study it to understand how genes for metabolism and stress response affect its ability to cope with environmental change.
Source: Wikipedia
Life cycle
Beetles at high elevations must survive long, cold winters and prolonged periods without food.
Source: Wikipedia
Where it comes from
The species is native to western North America.
Source: Wikipedia
Lookalikes
Comparisons with close relatives in the genus Chrysomela are available in a Canadian Entomologist review, helping to separate this species from similar beetles.
Source: Wikipedia
Where it is found in the US
Recorded in 7 of 51 states and DC. Most records: California, Colorado, Utah, Oregon, Washington, Alaska, Montana.
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
When are willow leaf beetles active?
Adults are active during the brief summer growing season from June through September, when they emerge, mate, and lay eggs.
Source: Wikipedia
How do the larvae defend themselves?
Larvae use chemicals taken from their host plant leaves to produce a defensive secretion that they release when attacked.
Source: Wikipedia
Same family (Chrysomelidae)
Spotted Cucumber BeetleDiabrotica undecimpunctataDamages trees, gardens or crops
Bean WeevilAcanthoscelides obtectusDamages trees, gardens or crops
Cowpea WeevilCallosobruchus maculatusDamages trees, gardens or crops
Swamp Milkweed Leaf BeetleLabidomera clivicollisDamages trees, gardens or crops
Alder Leaf BeetleAgelastica alniDamages trees, gardens or crops
Dogbane Leaf BeetleChrysochus auratusSources
- Wikipedia: https://en.wikipedia.org/wiki/Chrysomela_aeneicollis
Look it up elsewhere: GBIF · iNaturalist · BugGuide · ITIS · Wikipedia
Text written 2026-10-27 from the sources above and checked sentence by sentence against them. Data fetched 2026-10-27.