Adult Recognition
FWL: 8.0-10.5 mm
Forewing pattern is variable and Powell (1962) describes eight different forms. The most common forms are illustrated here. Most forms are also present in A. variana. Males lack a forewing costal fold.
Acleris gloverana is nearly identical to Acleris variana in both biology and morphology. The two species are geographically separated: A. gloverana occurs in western North America and A. variana occurs in eastern North America. Powell (1962) outlined minor genitalic differences that can be used to separate the two species. In males, the sacculus is broader and less elongate in A. gloverana, while it is narrower and more elongate in A. variana. In A. gloverana females, the sterigma is broad, with lobes connected, and a cestum is absent. In A. variana females, the sterigma is narrow with the lobes separate, and a weakly sclerotized cestum is present. In addition, females of A. variana have large abdominal scale tufts that are used to cover the eggs; these are lacking in A. gloverana females.
Larval Morphology
Larvae are approximately 11-15 mm in length and are green with a black head that turns brown in the final instar. The prothoracic shield is green to brown and heavily shaded with black on the posterolateral margins. An anal comb is present with 6-10 teeth.
Biology
Acleris gloverana completes one generation per year. Adults are present in late July through September.
Females lay single eggs on the underside of needles in the upper regions of host trees. Eggs overwinter until the following spring, and larvae hatch starting in mid-May. First instars feed inside opening buds, mid-instars web together needles to create a nest, and last instars are free-feeding. Males and 50% of females complete 4 larval instars while the remaining females complete 5 instars. Pupation occurs in webbed needles. Adults eclose in approximately two weeks.
This species can be a serious forest pest, and severe outbreaks can cover millions of acres. In coastal forests, extensive defoliation by A. gloverana can result in up to 50% tree mortality. Outbreaks tend to occur after periods of low rainfall.
Host plants
Acleris gloverana feeds on a variety of fir, hemlock, larch, and spruce.
| Family | Genus/species | Common name |
| Pinaceae | Abies balsamea (L.) Mill. | balsam fir |
| Pinaceae | Abies concolor (Gord. & Glend.) Lindl. ex Hildebr. | white fir |
| Pinaceae | Abies Mill. | fir |
| Pinaceae | Larix Mill. | larch |
| Pinaceae | Picea A. Dietr. | spruce |
| Pinaceae | Picea sitchensis (Bong.) Carriere | Sitka spruce |
| Pinaceae | Pseudostuga Carriere | Douglas-fir |
| Pinaceae | Pseudotsuga menziesii (Mirb.) Franco | Douglas-fir |
| Pinaceae | Tsuga Carriere | hemlock |
| Pinaceae | Tsuga heterophylla (Raf.) Sarg. | western hemlock |
Distribution
Acleris gloverana occurs from Alaska and northwestern Canada south to northern California and east to western Montana.
References
EPPO (European and Mediterranean Plant Protection Organization). 1997. Data sheets on quarantine pests: Acleris variana and Acleris gloverana. http://www.eppo.org/QUARANTINE/insects/Acleris_gloverana/ACLRSP_ds.pdf [accessed 7 March 2011].
Otvos, I. S. 1991. North American species in forestry, pp. 719-756. In L. P. S. van der Geest and H. H. Evenhius [eds.], Tortricid Pests: Their Biology, Natural Enemies, and Control. World Crop Pests, Vol. 5. Elsevier, Amsterdam.
Powell, J. A. 1962. Taxonomic studies on the Acleris gloverana-variana complex, the black-headed budworms (Lepidoptera: Tortricidae). Canadian Entomologist. 94: 833-840.
Powell, J. A. and P. A. Opler. 2009. Moths of western North America. University of California Press, Berkeley. 369 pp.
Photo Credits
Fig. 7: Edward H. Holsten, USDA Forest Service, Bugwood.org
Fig. 8: Tom Gray, Canadian Forest Service, Bugwood.org
