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Twolined larch sawfly

Twolined larch sawfly - Mature larvae, on western larch.
  • Latin name: Anoplonyx laricivorus (Rohwer et Middleton)
  • French name: Tenthrède bilignée
  • Order: Hymenoptera
  • Family: Tenthredinidae


British Columbia

This species occurs throughout the host range in British Columbia; it also occurs south to Oregon and Montana.



Damage, symptoms and biology

The twolined larch sawfly is a common, occasionally abundant and rarely destructive defoliator. Damaging outbreaks have not been recorded in British Columbia but have been recorded in Idaho and Montana.

Mature larva up to 14 mm long. Head, brown with black eyes. Body, green with a faint middorsal pinstripe, slightly broader faint subdorsal stripe and dark and somewhat broad supraspiracular stripe. Seven pairs of abdominal prolegs.

This species overwinters as a prepupal larva in a cocoon buried in the soil. Adults emerge from late May to June and the females lay eggs, usually singly, in needles. Larvae are present from mid-June to July. Mature larvae drop to the ground and spin cocoons from late July to August.

Canadian Forest Service Publications

Twolined larch sawfly

Diet and feeding behaviour

  • Phyllophagous : Feeds on the leaves of plants.
    • Free-living defoliator: Feeds on and moves about freely on foliage.
Information on host(s)

The twolined larch sawfly is restricted to western larch.

Main host(s)

Tamarack, western larch

Secondary host(s)

Engelmann spruce, lodgepole pine, ponderosa pine, Rocky Mountain Douglas-fir, western hemlock


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