Found on Young Pear Trees

Today when I visited our Community Orchard I found clusters of these creatures on three of our pear trees: they were surrounded by webs, part of which you can see here. They were identified by my former colleagues of Oaklands College, St Albans (formerly a County Agricultural & Horticultural College) as Pear Sawfly Larvae. As they were having a good go at the leaves on the trees I removed them.