Choristoneura conflictana (Walker) (Tortricidae: Tortricinae: Archipini)
Common name: large aspen tortrix
FWL: 12–17 mm
Head and abdomen gray to light brown, forewing similarly colored but fasciae darker, often brown. In some specimens, the banding is nearly obsolete; hindwing brown. Males lack a forewing costal fold.
Male genitalia are characterized by short, quadrate valvae with a well-sclerotized sacculus with an abruptly angular subapical projection on the ventral margin and a finger-like uncus (Dang 1992Dang 1992:
Dang, P. T. 1992. Morphological study of male genitalia with phylogenetic inference of Choristoneura Lederer (Lepidoptera: Tortricidae). Canadian Entomologist. 124: 7-48.). Female genitalia are characterized by a long, distally sclerotized ductus bursae and a hook-like signum with a large capitulum.
The following account is summarized from Prentice (1955)Prentice (1955):
Prentice, R. M. 1955. The life history and some aspects of the ecology of the large aspen tortrix, Choristoneura conflictana (Wlkr.) (n. comb.) (Lepidoptera: Tortricidae). Canadian Entomologist. 87(11): 461-473..
First instar larvae are 1.8–2.0 mm in length, with head, prothoracic shield, and anal shield light brown. The body is pale yellow green. During the third instar, the body color changes to grayish green and the head, prothoracic shield, and anal shield darken. Mature (fifth instar larvae) range in length from 15–21 mm and are usually dark green in coloration, sometimes entirely black.
A more detailed account of larval chaetotaxy is available in Prentice (1955)Prentice (1955):
Prentice, R. M. 1955. The life history and some aspects of the ecology of the large aspen tortrix, Choristoneura conflictana (Wlkr.) (n. comb.) (Lepidoptera: Tortricidae). Canadian Entomologist. 87(11): 461-473..
Choristoneura conflictana is unlikely to be confused with other Nearctic species of Choristoneura due to their distinctive gray wash to the forewing. Other species are almost always shades of brown or red. However, it can appear superficially similar to Amorbia cuneanum.
Choristoneura conflictana is primarily boreal in its distribution, being found almost anywhere trembling aspen naturally grows. In Canada, this corresponds to most areas except northern Quebec and the Northwest Territory. In the United States, C. conflictana reaches the southern limits of its range in New York, Indiana, California, and south through the Rocky Mountains to at least New Mexico.
The following account is summarized from Prentice (1955)Prentice (1955):
Prentice, R. M. 1955. The life history and some aspects of the ecology of the large aspen tortrix, Choristoneura conflictana (Wlkr.) (n. comb.) (Lepidoptera: Tortricidae). Canadian Entomologist. 87(11): 461-473..
In northern Manitoba and Saskatchewan, eggs are laid in flat clusters of approximately 60 to 450 eggs in mid June to early July. Larvae hatch in early to mid July, disperse, and feed gregariously on the epidermal layer of leaves of the host plant until mid to late August. Larvae molt once and overwinter as second instars in spun hibernacula under bark of the host tree. In the spring, second instar larvae emerge and re-ascend the tree to begin feeding again, usually in early to mid May, just before the aspen buds break. These larvae will then mine the aspen buds. Larvae molt to the third instar from within the bud. Once the non-damaged buds expand, larvae move out of the damaged buds and begin feeding externally by rolling leaves and feeding from within. This behavior is done throughout the third, fourth, and fifth (final) instars. Pupation occurs within a rolled leaf. Pupation occurs from early to mid June, with adults eclosing in mid June to early July after a pupal period of about 7–14 days, depending on weather conditions. Females deposit an average of 200 to 400 eggs in one or more clusters.
The preferred host for Choristoneura conflictana is quaking aspen (Populus tremuloides). In outbreak years, larvae have been recorded on several other broad-leaved trees because of lack of available quaking aspen. Severe to near complete defoliation of large stands of quaking aspen can occur, occasionally for several years in row.
View full screen host table here
Authors: KA Austin, TM Gilligan, ME Epstein
Content last updated May 2025
idtools.org
TortAI tool images at ipmimages.org - ITP Node
