Pale winged grey
- Latin name: Iridopsis ephyraria (Wlk.)
- French name: Arpenteuse à taches
- Order: Lepidoptera
- Family: Geometridae
Damage, symptoms and biologyThis insect has only recently been observed causing damage to eastern hemlock. In the first year of an outbreak, the larvae feed on the understory trees. They eventually move up into the crowns of mature trees over the next few years as the understory trees are stripped of their needles. When populations are high, they can completely defoliate and kill a tree within 2 years.
Missing or red foliage (needles), especially on the understory trees or lower branches of larger trees. Larval feeding during the early part of the season is on the new shoots, while later stages consume older needles.
The pale winged grey is a native insect found from Nova Scotia to Alberta. The hosts and distribution suggest that this is primarily a species of eastern hardwood forests.
There is one generation per year. It overwinters in the egg stage on the bark of trees. The eggs are approximately 0.68 mm long, elongate oval with a truncated end. When first laid, the eggs are greenish but later turn to a rusty colour. After hatching in June, the young larvae have a dark grey body with a rusty coloured head. This contrasts with the rear tip of the larvae, which tends to be yellowish. In the later larval stages, they become grey-brown to light-brown with very fine, ill defined markings on the body. There is a black spot on the side of the larvae just to the front of the middle of the body, often preceded by a small white patch. There are also four small black spots along the posterior half of the body. In July, the mature 22 - 26 mm long larvae drop to the ground and pupate. The pupae range from 10 to 11 mm long and 3 to 4 mm wide and are brown. They can be found just under the leaf litter to a soil depth of 10 cm, depending on soil compaction. The nocturnal adult moth emerges 13-20 days later to mate and lay eggs, and they are active during July until the middle of August. The female moth lays her eggs directly on the bark and not the foliage. The colour of the adults makes them very hard to see when they are resting on tree trunksand they blend in well with the moss and lichen.
Canadian Forest Service Publications
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