Robin’s pincushion growing on wild rose in the hedge along the Balk, Netherton. It is caused by the gall wasp Diplolepis rosae, which lays its eggs in a bud in springtime. The larvae develop in chambers in the gall and the next generation of gall wasps will emerge in the spring, almost all of them females. Males of this species are very rare but the females can lay fertile eggs without mating.
It’s also known as the bedeguar gall, from a French name which is derived from a Persian word meaning ‘brought by the wind’.