Someone's been eating my columbine!

Here it is all nice and filled out, ready to bloom.

Then these little buggers came along. I think they are sawfly larva.

In the morning this is what my columbine looked like after the had at it.

I fed them to the chickens after hand picking them off the leaves. Revenge! But there are probably still some munching away at it that I missed. I also tried a soap based spray, but seemed to have no effect. Blast!