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 metapleuron 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. In females, the basal sawteeth are diagnostic being pointed and strongly produced in semicolon and flattened in colon.
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
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]
Liston, A. D. 2016: Empria camtschatica Forsius and Tenthredo semicolon Mol (Hymenoptera: Tenthredinidae) in the British Isles. - The Entomologist's Monthly Magazine, 152: 131-135.
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
Taeger, A., 2013, The type specimens of Tenthredo Linnaeus, 1758 (Hymenoptera: Tenthredinidae) deposited in the Hungarian Natural History Museum, Zootaxa, 3626: 201–244.