Elaphrus
There are four British species all of the same general and very charactistic appearance and so distinct from all other British carabids. All are found near water. Our species are separated thus:
3 (1)	Elytra dull green. Prosternum hairy. Tarsi metallic green.	riparius Linnaeus
-	Elytra shining, dark metallic violet to (rarely) green. Tarsi metallic blue or violet. 8.5-10mm. Prosternum glabrous (the prosternal process may have scattered long setae)	cupreus Duftschmidt