Spangle galls on an oak leaf. Animated coloured scanning electron micrograph (SEM) of spangle galls on the underside of a leaf from the English oak (Quercus robur) tree. - HD 映像素材

These are fertilised eggs, which are laid by the female gall wasp Neuroterus quercusbaccarum. One leaf can have up to 100 of these galls, each containing a single developing larvae