A “lost” Rosemary beetle (Chrysolina americana) ; it is not often that one finds them on a plant other than their host plants. The Lamb’s-ear (Stachys byzantina) on which the beetle sits, grows next to a group of Salvia (Salvia sp.) plants. Days later two spikelets of the latter were occupied by two of the beetles. Possibly the specimen on the photo was on its way to the Salvia.
References1 Nederlands Soortenregister