Male genitalia of Choristoneura species from the Nearctic Region and Palaearctic Region are described and illustrated. The study revealed that the male genitalia are among the most important body parts that contain valuable morphological characters for species distinction or grouping in this genus. They are potentially useful in the clarification of the taxonomic status of species in closely related species groups, such as the spruce budworm species complex in North America.
On the basis of 17 interpretable male genital characters and their corresponding evolutionary states, the phylogeny of the genus Choristoneura is inferred and proposed. Nine species groups are recognized: (1) fumiferana, pinus, biennis, orae, occidentalis, lambertiana, carnana, retiniana, and spaldingiana; (2) diversana, murinana, metasequoiacola, and jezoensis; (3) longicellana; (4) lafauryana; (5) conflictana and fractivittana; (6) hebenstreitella, adumbratana, and luticostana; (7) albaniana and lapponana; (8) rosaceana and parallela; and (9) obsoletana and zapulata.
Morphological evidence obtained in the present study suggests that two conifer-feeding species groups of Choristoneura, species group 1 from the Nearctic Region and species group 2 from the Palaearctic Region, are related. They represent the least evolved species groups in the genus. Choristoneura rosaceana, C. parallela, C. obsoletana, and C. zapulata, representing some of the species feeding on deciduous trees, are among the most evolved Choristoneura species.