Andricus grossulariae

Andricus grossulariae is a type of tiny insect called a gall wasp. These little insects lay their eggs on the leaves of oak trees. When the eggs hatch, they release a chemical that causes the oak tree to produce a small bump called a gall. Inside this gall, the baby wasp will grow and develop until it's big enough to fly away.

Sometimes, Andricus grossulariae can lay their eggs on a different type of tree called a gooseberry bush. In this case, the gall that forms is a little bit different, but it still protects the baby wasp as it grows and develops.

So basically, Andricus grossulariae is a tiny insect that causes bumps to form on trees and bushes. It does this to protect its baby wasps while they grow.