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General DescriptionMature larvae are 20-22 mm long, yellowish brown with black heads. Adults with grey head and thorax, rarely reddish brown in females. Forewing typically gray with suffused, indistinct markings. Males occasionally and females more commonly have reddish brown hue. Hind wing uniformly dark brown or grayish black. Fringe whitish with dark basal line. Wingspan: males 21-26 mm, females 22-30 mm. For more detailed information see Freeman (1967). Color and pattern of the forewing can vary significantly and morphological resemblances among conifer-feeding Choristoneura make it very difficult to distinguish species using external morphological characteristics (Dang 1985). To identify species, other characters should be considered such as genitalia (Dang 1985, Dang 1992), mitochondrial DNA (Sperling & Hickey 1995) or behavioural characteristics such as host plant preference, larval diapause or pheromone attraction.