Trachelus tabidus - Black Wheat Stem-sawfly
Older records are widespread but come to an abrupt halt in 1959. Benson (1951) notes that the species is 'common in the fens' and says the larvae are a 'well-known pest of wheat, barley, rye and various wild grasses'. There seems to have been a catastrophic decline, apparently to complete loss. Whilst dedicated effort has not been put into searching for this species it seems highly unlikely that it would be entirely overlooked were it still present. Perhaps pesticides have been particularly effective against this species (Musgrove, 2022).
The smaller of the two Trachelus species. The second species, Trachelus troglodyta, is also extinct in Britain. The abdomen is black with a row of yellow flecks on lateral margins and the wings are grey with black veins and stigma. In Trachelus troglodyta the abdomen is banded with yellow and the wings are yellowish with yellow veins and stigma.
Trachelus tabidus larvae feed on cereals and grasses.
GB IUCN Status: Regionally Extinct
GB Rarity Status: Extinct
Distribution: England, Wales
Flight period: May to July
Plant associations: Cereal crops and wild grasses including Secale spp. (Rye grasses), Triticum spp. (Couch grasses).
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
Liston, A., 1995. Compendium of European Sawflies, Chalastos Forestry, Daibersdorf
Musgrove, A.J. 2022. A review of the status of sawflies of Great Britain - Phase 1: families other than Tenthredinidae. Natural England, unpublished