oriental chestnut gall wasp
A gall wasp native to China that attacks many Castanea species including the European sweet chestnut (C. sativa). The female is shiny black and up to 3mm long, while the adult male has never been seen. The eggs are produced by parthogenesis (ie. without fertilization). The larvae cause the bud to develop into a bulbous gall about 2cm across, which dry out after emergence and become woody The oriental chestnut gall wasp is the most serious pest of chestnuts around the world. It was first recorded in Britain in 2015.