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Western hemlock looper

Western hemlock looper - Lateral view of mature larva on western hemlock.
  • Latin name: Lambdina fiscellaria lugubrosa (Hulst)
  • French name: Arpenteuse de la pruche de l'Ouest
  • Order: Lepidoptera
  • Family: Geometridae


British Columbia



Damage, symptoms and biology

Hemlock looper damage usually occurs in mature stands where severe defoliation can result in growth reduction, top-kill and tree mortality.

This species overwinters as eggs laid on moss, lichens or bark. Eggs hatch from May to early June. The young larvae initially feed on the new foliage but as the larvae mature they feed on foliage of all ages. The larvae are wasteful feeders and leave behind partially consumed needles. Larvae are present from June to early September. Pupation occurs on foliage, or on tree trunks or in the duff from late July to early September. After a 10- to 14 day pupation, adults emerge and are in flight from September to October.

Mature larva to 30 mm long. Head, brown with eight prominent black spots. Body light to dark grey, complex pattern of alternating grey to cream-coloured longitudinal lines; four prominent dark spots on the dorsum of each abdominal segment.

Life cycle (West of the Rockies)

Life cycle (West of the Rockies)
Stage/Month J F M A M J J A S O N D

Other information

The western hemlock looper is one of the most destructive forest defoliators in British Columbia. Major outbreaks have occurred on the coast (on Vancouver Island and adjacent south coast in 1945-46) and in the interior wetbelt (upper Fraser River 1954-55, 1991-92; North Thompson-Wells Gray Park 1976 and 1991-92; Arrow Lakes 1972-73; Shuswap Lake 1983-84; Horsefly Lake-Quesnel Lake 1946, 1984 and 1991-92; and Revelstoke 1945-47, 1972-73, 1982-83 and 1991-93).

During outbreaks, this looper will also feed on understory shrubs.

Canadian Forest Service Publications

Western hemlock looper

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)

Main host(s)

Amabilis fir, Engelmann spruce, grand fir, Rocky Mountain Douglas-fir, Sitka spruce, subalpine fir, western hemlock, western larch, western redcedar, white spruce


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