Kidney vetch

I spent the afternoon looking for small blue butterflies with out success. Hopefully it is just too early as yet and they'll be flying in a week or two. They are very rare and we are lucky to have a small local population. They only feed on kidney vetch. There seemed to be a lot less of it this year.
I've added a couple of pictures of small blues I took with my phone in 2013. They aren't very blue, more blueish tinged mouse colour.