One of five Tenthredo species with a band of white antennal segments: colon, fagi, ferruginea, livida, semicolon. In colon and semicolon the white is confined to at most segments six to eight. The stigma of the forewing is unicolorous brown and the costa yellowish-brown. The scutellum is black and never white marked. The mesopleura and lateral face of the first tergite are each white marked. The head above is mostly impunctate and shining black.
Tenthredo semicolon has previously been confused with colon but can be separated by having less sculpture on the mesopleura and mesosternum giving semicolon a more shiny appearance.
Larvae are unknown.
Size: 10 - 12mm
Flight period: May? to August?
Plant associations: Unknown
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
Fekete, K. (2018) Beginner’s guide to identifying British Tenthredo, Natural History Museum, London. http://www.nhm.ac.uk/content/dam/nhmwww/take-part/identification-trainers/sawflies-guide-id-trainees.pdf [Accessed 26Apr2019]