Tenthredo baetica - Mustard Sawfly

First records of the species appeared around 1838-1840 when large numbers appeared on "common and white mustard" around Battersea and Hampstead before disappearing again. Benson (1952) was not aware of any records after 1895, although further infrequent records throughout the 20th century have since been unearthed. There appears to have been a recolonisation of East Anglia from 2019, with the species recorded from at least 12 locations to date since then, a number of which have been in arable farmland (suggesting it may be much more widespread). As a large and striking species, it is unlikely the species would have gone unrecorded in the intervening years unless it were absent or at an extremely low ebb (Musgrove, 2023).

This species is represented in Britain by the subspecies dominiquei (Konow, 1894). The antennae are subclavate (broadening in the mid to apical segments) with the basal two segments yellow. Body extensively marked with yellow. The wings are yellowish with yellow stigma and venation. In females the abdomen has yellow on the lateral apical margins on the basal tergites, with those marks becoming complete bands on tergites five and six. The apical tergites are mostly yellow. In males, tergites three to six are marked right across with red and all apical tergites mostly yellow.

Tenthredo baetica larvae feed on wild brassicas.

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Size: 10 - 12mm

GB IUCN Status: Least Concern
GB Rarity Status: Nationally Scarce

Distribution: England

Flight period: June to July

Plant associations: Brassica oleracea, Brassica nigra, Sinapis alba, Sinapis arvensis and Raphanus raphanistrum (wild cabbages, mustards and radishes)

References:

Benson, R.B., 1952. Handbooks for the Identification of British Insects. Hymenoptera, Symphyta, Vol 6, Section 2(a-c), Royal Entomological Society, London

Curtis, J. 1860: Farm Insects: being the Natural History and Economy of the Insects injurious to the Field Crops of Great Britain and Ireland, and also those which infest Barns and Granaries. With Suggestions for their Destruction. - Blackie and Son, Edinburgh [as Allantus flavipes].

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