One of two species in Britain. The tegulae are yellow and the pronotum is not edged with white behind. In Janus luteipes, the pronotum is edged with white and the tegulae are black or brown.
Larvae feed inside the twigs of oaks.
Flight period: May to June
Plant associations: Quercus (oaks)
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