It does seem to be a good year for blues. If you want holly blues, you need holly AND ivy, like FinedonDandy. It has an unusual lifecycyle - one generation of eggs is laid on ivy, the next on holly leaves. I've only got a couple of small, straggly hollies, but that and lots of ivy seems to do the trick. Mind you, in this part of Warwickshire, there are quite a lot of old field-hedges made of solid holly - very impressive.