In females, the abdomen is black except for an off-white hypopygium. The wing is infuscated up to the stigma and hyaline thereafter. At most, the basal one-half of the hind femora are dark, with the hind trochanter and trochantellus mainly pale. The tegulae are entirely dark.
The male thorax has the upper mesepisternum mainly pale. The antennae have 12 to 14 segments with the pedicel and scape being pale. The abdomen is black above but mostly pale below.
Larvae form blister mines in poplars, especially aspen.
Size: Females: 5 - 6.5mm, males: 4 - 5mm
Distribution: England, Scotland, Wales
Flight period: May to June
Plant associations: Populus tremula, Populus alba and Populus nigra (aspen, white and black poplar)
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
Liston, A., Mutanen, M. and Viitasaari, M., 2019. On the taxonomy of Heterarthrus (Hymenoptera, Tenthredinidae), with a review of the West Palaearctic species. Journal of Hymenoptera Research, 72, p.83.