Sirex noctilio Fabricius, 1793

Sirex noctilio

A black bodied wood wasp with mostly reddish-yellow legs, though femora may be darker. The apical tarsal segments are dark. The sawsheath is shorter than the oblong ventral plate from which it arises. The ovipositor has large pits along its length separated from each other by their own length at the mid-point. The mesopleura are densely punctured with the spaces between, smaller than the punctures. In certain light the mesopleura and abdominal tergites are iridescent violet.

Females live for about 3 weeks and once they have mated, they look for weak and stressed pine trees to lay their eggs in. A female can lay several hundred eggs. Using their tough, needle-like ovipositor they drill into the heartwood of the selected tree. The ovipositor is strengthened by having zinc within the outer layer. Having drilled into the tree the female then inserts a mixture of toxics, to further weaken the tree, and fungal spores (Amylostereum areolatum) that grow and feed on the wood fibres. It is the fungus and rotting wood that the larvae then feed on. It can take up to three years for the larvae to grow and the emerging new adult females will collect some of the fungal spores into special glands prior to flying off to start the next generation.


Size: 14 - 30mm

Status: Insufficient data

Distribution: England, Scotland, Wales, Ireland

Flight period: Late summer

Plant associations: Pinus spp. (pines)


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.

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