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Hemlock looper

Hemlock looper - Mature larva on fir twig (length: 32 mm)
  • Latin name: Lambdina fiscellaria (Guenée)
  • French name: Arpenteuse de la pruche
  • Order: Lepidoptera
  • Family: Geometridae




Leaf, Needle

Damage, symptoms and biology

Hemlock looper damage is visible on conifers during epidemics in late July and early August. The trees turn a reddish colour, which is very characteristic of hemlock looper outbreaks. Needles damaged by feeding larvae dry out, turn red and drop in the fall.

Hemlock looper outbreaks develop and subside very suddenly. They spread quickly and can cause the death of balsam firs in the first year that damage is detected.

The wasteful feeding of this species and its rapid population growth make it a serious defoliator.

There are four or five larval stages, depending on the region of Canada. When mature, the larvae look for a pupation site. During heavy infestations, trees are covered with silk strands produced by the larvae as they descend the tree trunks in search of food or pupation sites.

The insect has only one generation a year and overwinters in the adult stage.

Life cycle (East of the Rockies)

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

Other information

Native to North America, the hemlock looper is considered a serious defoliator in Canada. It occurs from the Atlantic coast west to Alberta. It has destroyed several million hectares of conifer forests in eastern Canada over the years. The other subspecies, Lambdina fiscellaria lugubrosa (Hulst,) is found in British Columbia. The main hosts of this insect are balsam fir in eastern Canada and hemlock in western Canada.

Between 1910 and 1975, hemlock looper outbreaks caused timber losses estimated at 12 million cubic metres in Newfoundland and 24 million cubic metres in Quebec. Since then in Quebec, infestations in the Lower St. Lawrence, Gaspé Peninsula, Anticosti Island and, most recently, the North Shore, have also resulted in timber losses.

In Quebec, the insect is being monitored by the ministère des Ressources naturelles, de la Faune et des Parcs du Québec and the Société de protection des forêts contre les insectes et les maladies (SOPFIM) to prevent further invasions. During severe epidemics, aerial spraying of the biological insecticide Bacillus thuringiensis var. kurstaki (B.t.k.) is carried out to control hemlock looper populations. This is the product that has most commonly been used over the past decade.

Several natural enemies, including parasitoids, play an important role in hemlock looper population dynamics.

In the presence of a severe infestation that is limited to small areas, infested stands and adjacent stands can be harvested over the winter, even if major losses are anticipated.

Canadian Forest Service Publications

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)

Balsam fir, black spruce, eastern hemlock, sugar maple, white birch, white spruce


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