One of two species in Britain. The tegulae are black or brown and the pronotum is edged with white behind. In Janus cynosbati, the tegulae are yellow and the pronotum is not edged with white.
Larvae feed inside the shoots of willows, poplars, etc.
Status: Locally common.
Distribution: England, Wales
Flight period: May to July
Plant associations: Salix (willows), Populus (poplars), Viburnum (wayfarer, guelder rose).
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