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Western larch sawfly

Western larch sawfly -
  • Latin name: Anoplonyx occidens Ross
  • French name:
  • Order: Hymenoptera
  • Family: Tenthredinidae


British Columbia

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



Damage, symptoms and biology

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

Mature larva up to 21 mm long. Head, brown with black eyes. Dark grey dorsum except for a light grey middorsal stripe; light grey below the spiracular line. 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

Western 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)

Western larch sawfly is restricted to western larch.

Main host(s)

Tamarack, western larch

Secondary host(s)

Black spruce, Engelmann spruce, lodgepole pine, western white pine, white spruce


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