The two Diprion species can only reliably be distinguished by the saw teeth and the penis valve since the external features of both are variable. Both species are yellowish with various degrees of black on the head, mesonotum, mesosternum and tergites 3 to 6. Diprion pini females have saws with irregularly spaced and sized teeth. The penis valve is only shallowly sinuate on the serrated edge.
Larvae of the two species are easily recognisable and each feeds communally on pines. Larvae prefer mature needles from previous years' growth. Temperature affects the phenology and in hot, dry years a second generation can arise leading to population surges. Climate change could result in significant defoliation outbreaks. Under normal univoltine conditions larvae form cocoons in autumn in the leaf litter or just below. However, in bivoltine years, the larvae make their cocoons in the crowns of pine trees. Second generation adults emerge after a short duration in late July. Larvae arising from this second generation feed on the current year's needles.
Size: 7 - 10mm
Distribution: England, Scotland, Wales, Ireland
Flight period: Univoltine May to July, or bivoltine in hot years May to July, July to August
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. https://doi.org/10.3897/BDJ.2.e1168
Möller, K., Hentschel, R., Wenning, A. and Schröder, J., 2017. Improved outbreak prediction for common pine sawfly (Diprion pini L.) by analyzing floating ‘Climatic Windows’ as keys for changes in voltinism. Forests, 8(9), p.319.