Eriocampa ovata - Woolly Alder Sawfly

A common and easily-recognised species in both adult and larval stages, occurring widely across most of mainland Britain (Musgrove, 2023).

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. In Eriocampa ovata the sides of the thorax are black and heavily punctured. Males are extremely rare. Mid and hind tibia whitish about the knees.

Eriocampa ovata 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

GB IUCN Status: Least Concern
GB Rarity Status: None

Distribution: England, Scotland, Wales, Ireland

Flight period: Univoltine (possibly bivoltine) May to August

Plant associations: Alnus glutinosa (alder)


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.

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.

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 Natural England, unpublished

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.