Bug FAQBlue Dock Beetle
Gastrophysa cyanea · Order: Coleoptera · Family: Chrysomelidae
Also called: Green Dock Beetle
The blue dock beetle is a tiny 4-5 mm beetle that is metallic green, and some preserved specimens can turn a metallic blue. It lives in North America, emerges in spring, and the adults feed on curly dock plants.
Source: Wikipedia
How to recognize it
Adults are metallic green, and some pinned specimens may change to a metallic blue color.
Source: Wikipedia
Size
They measure about 4 to 5 mm in length.
Source: Wikipedia
Where it lives
They are found throughout North America.
Source: Wikipedia
What it eats
In spring they commonly feed on curly dock.
Source: Wikipedia
Life cycle
Adults emerge in the spring.
Source: Wikipedia
When you see it
Their activity peaks in spring.
Source: Wikipedia
Where it comes from
Their native range is North America.
Source: Wikipedia
Where it is found in the US
Recorded in 32 of 51 states and DC. Most records: California, Kentucky, Utah, Texas, Colorado, New Mexico, Pennsylvania, Kansas.
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
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/Gastrophysa_cyanea
Look it up elsewhere: GBIF · iNaturalist · BugGuide · ITIS · Wikipedia
Text written 2026-10-24 from the sources above and checked sentence by sentence against them. Data fetched 2026-10-24.