Green dock beetle seems such a plain name for such a beautiful little creature as this. Even its scientific name, Gastrophysa viridula, makes it sound like a brand of effervescent stomach-acid relief tablet. I think it should be renamed Rainbow dock beetle, as the metallic sheen of its green wing casings makes it appear blue, purple, red, turquoise or even gold, depending on the light.
At around 4mm long, Mr GDB is smaller than Mrs GDB, who is usually around 7mm, and he looks even smaller when the female’s body becomes swollen during pregnancy. She expands so much even her wing cases won’t fit properly.
As you can surmise from their name, these little beetles live on dock plants and are easily spotted in the months of May and June, if not by that iridescent shimmer, then from all the little holes they make in the dock leaves. Turn over a leaf and you’re likely to find little clusters of yellow-orange eggs or, if you’re lucky, a little group of the next generation, the little dark-greyish larvae. These will eventually pupate underground, then between 7-10 days later the adult beetles will emerge to start the cycle all over again.