Unknown gall 1

Unknown gall 1

Observation - Unknown gall 1. Description: There were three of these galls on this tree, which I believe is wytch elm. They appeared to have been formed from the previous years leaf buds on the tips of twigs and were approx 50mm in diameter.When found they were hard and dry, completely hollow and

There were three of these galls on this tree, which I believe is wytch elm. They appeared to have been formed from the previous years leaf buds on the tips of twigs and were approx 50mm in diameter.When found they were hard and dry, completely hollow and had a shell wall approximately 2mm thick. Inside the hollow was what looked like caterpillar fras and there were a number of holes in the shell where the occupants may have exited.
Any ideas on this one would be appreciated.