Hemlock Looper

Order: Lepidoptera

Family: Geometridae

Latin Name: Lambdina fiscellaria fiscellaria (Guen.)

Common Names: Hemlock Looper


The hemlock looper is an insect native to North America, occurring from the Atlantic coast west to Alberta and Iowa. In the west, its normal preferred diet is eastern hemlock and in the east, balsam fir. During periodic outbreaks it will feed on other conifers, hardwoods, and will even resort to cannibalism when the food supply is scarce.

Hemlock looper eggs are about 0.9 mm in length and football-shaped. The colour of the egg tells whether it is fertilized (golden brown), unfertilized (green), or parasitized (black).

The larva of the hemlock looper has a cylindrical smooth shape, no bristles or hairs, and a characteristic "looping" or "inching" movement. Young larvae are dark grey but as they mature their colours can range from yellow to black. Full grown larvae are 32mm long.

Life History

The hemlock looper has one generation per year and overwinters in the egg stage. Upon hatching in June, the newborn larvae are attracted to light and immediately move toward the tender needles of the new shoots. This food is absolutely necessary to their survival. Should this food be lacking, they may starve or eat each other.

As they grow, the larvae begin to feed on older needles. Defoliation levels may be irregular throughout the crown as well as in the forest. During an outbreak in a given area, severely defoliated stands can be found next to unaffected stands.

Larval development is completed in July and August. The larvae then become repelled by light and seek a shaded area to pupate. This is why the pupae are most often found in bark crevices, lichens, or under dead leaves, bark or other debris. The pupal stage lasts 15 to 20 days. The first few moths will be seen around the middle of August with the bulk of the moths flying around the middle of September.

Damage Symptoms and Population Limiting Factors

The young larvae prefer to eat the new foliage, whereas the older larvae eat both new and old foliage. They are wasteful feeders. The larvae bite pieces out of the needles without consuming them completely. This feeding habit can quickly defoliate a tree. Heavy defoliation for more than one year usually results in the tree's death.

Small numbers of hemlock looper occur naturally in all fir and spruce forests in Nova Scotia. When ideal conditions exist in mature and over-mature stands, their population builds to epidemic levels causing severe defoliation and tree mortality. Serious outbreaks of hemlock looper appear suddenly but rarely last more than a few years. It is thought that these sudden population collapses are due to a rapid build-up of parasites and disease which act as a natural biological control.

The flight capabilities of adult moths are extremely poor. This may limit their expansion into new feeding areas and may explain why looper populations build in small areas then suddenly collapse. The close quarters and lack of food promote starvation and disease. Moths fly at any time of the day but are particularly active in the evening when the male is seeking the female. Moth flight activity can last into November.

Control Options

Harvest stands of overmature fir and spruce to remove potential population build up sites. Biological control products are recommended for large forested areas. These will not interfere with naturally occurring parasites and diseases that help control looper populations.

For ornamental fir, both biological or contact insecticide can be used. When using a biological insecticide such as Btk, the product should be applied while the larvae are in the open and feeding.


CAUTION: Read and follow the instructions on the label when using any control agent. Proper application and use of recommended personal protective equipment are essential for the safe use and effectiveness of any pesticide.

DISCLAIMER: Control options are suggestions only. Actions taken for pest control are the sole responsibility of the applicator in full compliance with any Federal, Provincial or Municipal Acts, Regulations or Bylaws.