Ynghylch

The oak marble gall wasp, Andricus kollari, is a tiny wasp that causes galls on oak leaves. Clusters of oak marble galls (also known as 'oak nuts') can be found on oak twigs. They turn brown as they mature and emergence holes, from which the asexual adults have escaped, can be seen from autumn onwards. The empty gall is left on the twig. The emerging females then lay eggs in the buds of Turkey oaks, which develop overwinter and emerge in spring as a sexual generation of males and females, ready to make the familiar summer gall.