Overall, a black insect with reddish-yellow legs which may be infuscated on the apices of the tibiae and tarsi. In the male, the tegulae, underside of the antennae and the hypopygium are brown. In the female, the edge of the pronotum and more or less the underside of the abdomen are brown. Sawsheath not projecting as far back as the long cerci.
Platycampus luridiventris larvae are unmistakable, being flattened against the leaf surface. They feed on alders and develop slowly, often to be found well into October. They make oval feeding holes in the leaf blade. In captivity, the final instar may cocoon in leaves or burrow into the substrate. The larva becomes an eonymph within the cocoon but prior to cocooning will empty its gut and holds its head in a more upright position.
Size: 5 - 6mm
Distribution: England, Scotland, Wales, Ireland
Flight period: May to June
Plant associations: Alnus spp. (alders)
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