Fractionated extracts of foliage of juvenile jack pine, Pinus banksiana Lambert, were investigated as antifeedants for larvae of the Swaine jack pine sawfly, Neodiprion swainei Middleton, and N. rugifrons Middleton. A partially purified fraction exhibiting strong antifeedant activity was obtained from aqueous extracts by a selective extraction procedure and by TLC. This fraction had similar TLC development and IR spectral absorption as an antifeedant component in a hexane extract of juvenile foliage. N. swainei showed variable feeding preference to non-host foliage and oleoresin extracts. Several non-oxygenated monoterpenes common in pine needle oil did not inhibit larval feeding. Terpene acetates also were inert. The resin acid, 1-pimaric, did not inhibit N. rugifrons feeding; d-pimaric acid and abietic acid were not active at low concentration (1%), but deterred larval feeding at a higher concentration (20%). Larvae were strongly deterred by tall oil fatty acids and certain oxygenated monoterpenes. Feeding of both sawflies was inhibited by certain quinoidal compounds; larvae were most sensitive to 2-methyl-3-phytyl- 1,4-naphthoquinone > 5-hydroxy-1,4-naphthoquinone > 1,4-naphthoquinone > 2-methyl-1,4-naphthoquinone > 2-hydroxy-1,4-naphthoquinone.