Common Spangle GallMacro Art
Image details - Common Spangle Gall
If you've ever looked at the underside of an oak leaf, you may have found these odd looking structures that are a few millimetres across. They are common spangle galls caused by a small wasp (Neuroterus quercusbaccarum ). The wasp lays an egg on the leaf and as the egg hatches the larva tricks the oak leaf into producing this structure for it to live in and feed on. In the autumn the gall drops off the leaf and the wasp continues its bizarre life cycle.