Tenthredo ignobilis - Roseroot Sawfly

Undiscovered in Britain until 2010, when multiple individuals were found in Perthshire, at Meall nan Tarmachan (Ben Lawers NNR) and Bridge of Garry (near Pitlochry). At time of writing, no subsequent records have come to light from similar upland habitats, so it is still uncertain as to whether this is a very localised species, or widespread but overlooked in upland habitats (Musgrove, 2023). 

One of the Tenthredo atra group (atra, ignobilis, moniliata) that may require further revision. Tenthredo ignobilis was identified as present in Scotland by Liston et al following collecton of samples in 2010. This species was previously considered as a colour morph of atra. The Scottish specimens differ slightly from European examples. Tenthredo ignobilis has a black stigma and apex of costa (brown in moniliata). In the female the tegulae are black (red in moniliata) and the mesepisterum in males is ventrally completely black (also black in atra, but largely red in moniliata). In females the abdomen is marked red on tergites three to five and occasionally the extreme margins of two and six (female abdomen entirely black in atra).

Tenthredo ignobilis larvae feed on stonecrops. The likely foodplant at the former mentioned locations is Roseroot, Sedum rosea, which is widespread in the Highlands.

Jump to other species of Tenthredo

Size: 11 - 12mm

GB IUCN Status: Data Deficient
GB Rarity Status: Nationally Rare

Distribution: Scotland

Flight period: May to August

Plant associations: Sedum telephium and Sedum rosae

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

Liston, A.D., Knight, G., Heibo, E., Bland, K.P., Barstad, T.E., Blank, S.M., Boevé, J.L., Fiedler, C., Grearson, K.J., Halstead, A. and Jacobs, H.J., 2012. On Scottish sawflies, with results of the 14th International Sawfly Workshop, in the southern Highlands, 2010 (Hymenoptera, Symphyta). Beiträge zur Entomologie= Contributions to Entomology, 62(1), pp.1-68.

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