More bugs!!!

Hi everyone. The bugs are against me this year. I have just spotted this morning that my pear tree at home is being attacked by caterpillars. It has had fire blight already the last couple of year but seems (fingers crossed) to have survived it and now it is having its top leaves munched!

Can anyone tell me what caterpillars these are? I've never seen ones like this before. They are sat in the top of the tree and there is a lot of silk around them.

Also am I going to have to don the rubber gloves and squish them?

Thanks