A gall of <i>Andricus grossulariae</i> fallen from a tree of <i>Quercus robur</i> at the National Botanical Garden of Belgium
<a href="//commons.wikimedia.org/w/index.php?title=User:Qgroom&amp;action=edit&amp;redlink=1" class="new" title="User:Qgroom (page does not exist)">Quentin Groom</a>
CC BY 1.0
<span class="int-own-work" lang="en">Own work</span>