Gastrophysa (Gastrophysa) cyanea F. E. Melsheimer 1847

Adults emerge in April (Lawson 1950) varying somewhat by region but being present at least until August (McCracken 1906, Strickland Collection).

According to Lawson, these beetles are found throughout southern Canada and the United States (1950). The Strickland collection includes specimens collected in the Northwest Territories as well as the southern half of Alberta.

Larvae have few spines, their bodies change from yellow to black to green throughout their instar stages. A diagram from Lawson shows their bodies as being spotted. Their head capsules are dorso-ventrally flat and usually darker than their bodies (Lawson 1950). Two known colour morphs of adults exist, one metallic green and one black with a metallic blue sheen (McCracken 1906). No difference appears to exist between the two adult colour morphs (Lawson 1950), however all beetles start out as black, while those with a recessive gene later develop green colouration (McCracken 1906).They have fewer tiny depressions spread over the head and thorax compared to the elytra which are very punctate. They are 4-5 mm in length and are oblong oval in shape. Their sternites, antennae, and legs are purplish black (Blatchley 1910).

May have similar habitats as G. polygoni and G.viridula which are often found in cultivated areas with homogenous plant communities (fields of hay or cereals, yards).

Pupation occurs in the soil (Lawson 1950).They may be multivoltine, similar to G. viridula .

Herbivorous on Rheum rhabarbarum (rhubarb) and several species within the plant genus Rumex (dock) (Lawson 1950).

Gastrophysa cyanea, the green dock beetle (note: Gastrophysa viridula in Europe is also sometimes called the green dock beetle), is a species of leaf beetle in the family Chrysomelidae. It is found in North America. G. cyanea is 4-5 mm and metallic green. Females can be distinguished by their swollen abdomens prior to egg laying. They emerge in spring and commonly feed on curly dock. Some pinned specimens will turn metallic blue.