Tenthredo mandibularis - Butterbur Sawfly

Recorded locally through mainland Britain north to around Dundee; relatively infrequent in the south (Musgrove, 2023).

The only Tenthredo species where the whole body and hind legs are entirely black in both sexes. The head, including the clypeus, is also black, but the base of the mandibles is white. Although not mentioned in the literature, many specimens have a white fleck on the lateral face of the first tergite.

Tenthredo mandibularis larvae feed on coltsfoot and butterbur. The larvae are similar to Tenthredo thompsoni. However, thompsoni doesn't have the white warts inside the yellow spots that are present in mandibularis. 

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Size: 13 - 14mm

GB IUCN Status: Least Concern
GB Rarity Status: None

Distribution: England, Scotland, Wales

Flight period: June to August

Plant associations: Petasites hybridus (butterbur), Tussilago farfara (coltsfoot)

The National Biodiversity Network records are shown on the map below. (See terms and conditions)

References:

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, 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

Musgrove, A.J. 2023. A review of the status of sawflies of Great Britain - Phase 2: The Athaliidae and the Tenthredinidae (excluding Nematinae). Natural England, unpublished