Sirex torvus - Grim Woodwasp

This is a species of Central European origin and is not thought to be the same species at S. cyaneus. Schiff et al. (2012) split the Nearctic cyaneus from the European torvus and only torvus was included in the British Checklist by Liston et al. (2014). However, it is not clear how many specimens were redetermined following this taxonomic change. Torvus is very close in appearance to atricornis which it seems may be present in northern Scotland. Reports of the aggregated torvus/cyaneus species-pair have come from each of England, Scotland and Wales. Records are very sparse recently, with one in 2013 being the only 21st century record at time of review (Musgrove, 2022).

Sirex torvus females have the sawsheath longer than the basal plate (as described in Benson) whereas S. cyaneus has the sawsheath equal in length to the basal plate.

The female is blue-black with reddish yellow legs and is similar to S. juvencus. However, the basal segments of the antennae are always black.

Males differ from the female in having darker hind legs and an abdomen that is reddish brown from tergite 3 to the apex.

Sirex torvus larvae feed in the timber of fir trees for up to 3 years.

Jump to other Sirex species

Size: 10 - 40mm

GB IUCN Status: Data Deficient
GB Rarity Status: Unclear

Distribution: England, Scotland, Wales, Ireland

Flight period: June to October

Plant associations: Abies spp. (firs)

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

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. 2022. A review of the status of sawflies of Great Britain - Phase 1: families other than Tenthredinidae. Natural England, unpublished

Schiff, N. M., Valley, S. A., LaBonte, J. R. and Smith, D. R. (2006) 'Guide to the siricid woodwasps of North America.' Forest Service, Forest Health Technology Enterprise Team. USDA, Morgantown

Viitasaari, M. & Midtgaard, F. 1989: A contribution to the taxonomy of horntails with notes on the genus Sirex Linnaeus (Hymenoptera, Siricidae). - Annales Entomologici Fennici, Helsinki 55(3): 103-110