Chermes lariciatus was described by Patch from the gallicola migrans and further information on this form was given by Annand under the genus Adelges. The complete polymorphic cycle on spruce and larch is described here, with information about the life history, habits, seasonal development, and morphology. Fundatrices overwinter as nymphs below new buds of spruce on 1-year-old needle bases. Gallicolae develop in early summer within galls which are globular in shape and usually only partly surround the twigs. Sistentes overwinter as first-instar nymphs on larch buds, wedged among the bases of the needles or scales, with the heads up and the mouth parts inserted into the bud. The progredientes and sexuparae move to the new cones in early summer when there is a cone crop, but settle on the leaf buds when there is none. Sexuales nymphs on spruce remain under the parent sexuparae during development. A diagrammatic representation of the seasonal development and a description of the morphology of the first-instar nymph and adult of each form is given. A discussion concerning the validity of this and related species is included.