This Asiatic species was first confirmed as present in Britain in 2017. However, it is thought to have been present for some time previous to this. It is multi-generational and able to increase in number rapidly. Only females are known. Adults are black with pale legs and the membranes between sclerites appears greenish. Head shape changes between first spring generations and subsequent generations. It is thought that this is due to the muscle requirements needed to break the winter cocoon compared to the more flimsy summer coccoons.
Larvae feed on most elms and the small green larvae carve out a characteristic zig-zag channel between the leaf veins as it feeds. This pattern breaks down as the larvae matures and the leaves become skeletonised in appearance. Golden coccoons can be found on the underside of leaves, though autumn generations pupate in the ground.
Size: 5 - 6mm
Status: Common and becoming widespread
Flight period: Multivoltine, April to October
Plant associations: Ulmus spp. (elms)
Benson, R.B., 1952. Handbooks for the Identification of British Insects. Hymenoptera, Symphyta, Vol 6, Section 2(a-c), Royal Entomological Society, London
Liston A, Knight G, Sheppard D, Broad G, Livermore L (2014) Checklist of British and Irish Hymenoptera - Sawflies, ‘Symphyta’. Biodiversity Data Journal 2: e1168. https://doi.org/10.3897/BDJ.2.e1168