A couple of days ago I was surprised to come across this small green chalcid wasp. It was probably a Torymid wasp (Hymenoptera: Torymidae), similar to the ones that I saw in October (see here and here). However, back in October they were on oak leaves, which have now all gone; this one was on an ivy leaf (Hedera helix). Whether this means its must be a different species, I don't know.
Photo taken in Whiteknights Park, Reading University grounds, Reading, UK, on 2009-12-12.