Abstract
Based on multivariate morphometric analysis of variation among populations in North America, three subspecies of balsam woolly aphid, Adelges piceae (Ratzeburg), are described and illustrated: A. piceae piceae (Ratzeburg), A. piceae canadensis (Merker and Eichhorn), and A. piceae occidentalis, subsp. nov. Diagnostic characters of the 1st instar and the adult and a key to the North American subspecies are provided.

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