At this time of year you sometimes see lots of hawthorn hedgerows covered in silken webs, on closer inspection you'll find millions of little caterpillars stripping the leaves and spinning the silk all over the hedgerow, this year its particularly noticeable. There are a number of caterpillars that can do this including various species of ermine moth and hawthorn moth caterpillars.
Its an incredible sight to see and I've seen miles of hawthorn stripped by these little monsters, however it's part of the creation cycle and the hawthorn will replenish.