Rare and known only from Britain. A black sawfly within the tibiale group of very similar Trichiosoma species. It has been hypothesised that this species may be abdormal dwarf specimens of Trichiosoma tibiale. No key available at this time.
Trichiosoma pusillum larvae feed on willows.
Size: 13 - 24mm
Flight period: May to June
Plant associations: Salix spp. (willows)
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
Viitasaari, M. 1989: Taxonomic notes on the genus Trichiosoma Leach (Hymenoptera, Cimbicidae) II. - Annales Entomologici Fennici, Helsinki 55 (3): 111-129