I was cycling around Puglia enjoying the countryside for a week earlier this year while The Puffin Whisperer was working. There were birds, butterflies, lizards, flowering cherry trees, quinces and amazing stone walls; plenty to keep me occupied:
One thing I saw puzzled me though; looking up into the blue sky I saw what looked like a growth on this oak tree:
Searching around I found some on the ground:
They appeared to be growing out of the acorn cups. My first thought was that they must be galls; the excessive defensive reaction to having the eggs or grubs of insects inside them. There are 380 different species of Cynipid gall wasp in Europe alone. Then I thought it might be a viral or some other attack, like the ‘witches-broom’ which attacks trees.
After my failure to identify it The Puffin Whisperer came up trumps and spotted that it was the Oak Medusa Gall, Andricus caputmedusae:
What a tangle.