Caterpillar (Large White)

There have still been very few butterflies around here this year, but today I was pleased to find caterpillars on my cabbages.  The main picture is the biggest one I found; the other two are very recently hatched clutches.  I'm not worried about them eating my cabbages. I've been checking fairly regularly, because there are lots of holes in the leaves, which up until now must have been caused by slugs.  (There's no shortage of them!)