From back in April: a pair of brassica bugs, Eurydema oleracea (Hemiptera: Pentatomidae) mating on a garlic mustard (Allaria petiolata) leaf. These bugs come in black and white, black and red, and black and yellow variants. I have seen all three variants on the same plant.
A black and yellow one from a few days earlier:
And from a recent walk, what I think is a nymph of the same species:
This was on a mullein plant (Verbascum thapsus) but still only a few metres from where I saw the above specimens. The stand of garlic mustard had by then gone to seed and its leaves had turned purple.
Photos taken in the field below Chazey Wood, near Caversham, UK, on 2011-04-24, 2011-04-17 and 2011-07-11, respectively.