Curculio villosus boring into an oak apple
Curculio villosus boring into a gall ("oak apple") on Oak caused by the gall wasp Biorhiza pallida, to later insert an egg into the gall.
This is an example of "secondary" usage of the gall body, by another organism than the one causing the gall in the first place.
Curculio villosus Fabricius, 1781 is a small weevil closely related to the more well known Acorn weevil (Curculio glandium) and Nut weevil (Curculio nucum) but bores its eggs not into the fruit body of the tree, but in gals on oak caused by the sexual generation of the gal wasp Biorhiza pallida. The larva of the wasp usually perishes because of food competition.