The red-backed alder sawfly. A distinctive species with a blood red top to the thorax and heavily punctured black sides and head. Similar to Eutomostethus ephippium which is much smaller and has red sides to the thorax. Males are extremely rare. Mid and hind tibia whitish about the knees.
Adults prefer to remain around young alders. Eggs are laid into the leaf midrib. Larvae have an external accumulation of a white, woolly, wax coat and feed on alder preferring matured leaves. Larvae have five to seven instars and take three to four weeks to develop. Eonymphs drop to the ground and form a cocoon in the ground usually close to the trunk of the sapling about 5cm below ground. It is possible that some individuals emerge as adults three to four weeks later, whilst others overwinter as prepupae (Mackay and Wellington, 1977).
Size: 5 - 7mm
Distribution: England, Scotland, Wales, Ireland
Flight period: Univoltine (possibly bivoltine) May to August
Plant associations: Alnus glutinosa (alder)
The National Biodiversity Network records are shown on the map below. (See terms and conditions)
Benson, R.B., 1952. Handbooks for the Identification of British Insects. Hymenoptera, Symphyta, Vol 6, Section 2(a-c), Royal Entomological Society, London
Borden, J.H. and Dean, W.F., 2019. Observations on Eriocampa ovata L.(Hymenoptera: Tenthredinidae) infesting red alder in southwestern British Columbia. Journal of the Entomological Society of British Columbia, 68, pp.26-28.
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
Mackay, P.A. and Wellington, W.G., 1977. Notes on the life history and habits of the red-backed sawfly, Eriocampa ovata (Hymenoptera: Tenthredinidae). The Canadian Entomologist, 109(1), pp.53-58.
Pieronek, B., 1980. On the larval Eriocampa ovata (Linnaeus) feeding on alder (Hymenoptera: Tenthredinidae-Blennocampinae). Mitteilungen aus dem Zoologischen Museum in Berlin, 56(1), pp.85-89.