Here is what the hungry buggers look like, you can see them bunched together in their caterpillar form. The green bits is caterpillar poo.
In previous year the infestations were bad, at night time you could stand underneath the tree and hear them munching on the leave. At one point my neighbour even complained to me that the blighters were keeping him awake at night. They could strip the tree bare in under 2 weeks, (we are talking about a large tree here). They would make there way into the house, and bingo some weeks later we had moths to contend with. Fingers crossed I've not seen any in the house this time.