What is that?

OK, it's payback time. We entertain you and now you do a bit of work for us. Gill was grossed out by the following bug or grub or maggot or whatever that she found in the girls' run his morning. Poked with a stick it curled up. Uncurled it was about 4-5 inches (10-12cm) long. It was faintly irridescent. It left the run some time later - possibly pushed out by the dogs. So, what was it?