Pacific Northwest Moths

Identification

Adults

Brachylomia obscurifascia is a small, powdery gray moth (FW length 13 mm) that flies in eastern Oregon during the fall. It has a short basal dash, pale-filled gray transverse lines, black-rimmed orbicular spot, a pale-filled reniform spot, and a gray spot near the anal angle. The ground color is powdery mottled gray, slightly darker along the costa, in the median area, and in the anterior half of the subterminal area and lightest in the posterior subterminal area. An ill-defined gray spot is present in the posterior terminal area. A short black basal dash is present. The basal, antemedial, and postmedial lines are gray, double filled with the ground color or light gray, often whitish posterior to the cubital vein. The basal line is evident on the costa. The antemedial line is slightly irregular, nearly straight across the wing with a short concave segment across the cell. The median line is diffuse gray, faint to moderately prominent. The postmedial line is stronger than the other lines and has paler gray filling. It is weakly toothed on the veins, drawn sharply toward the base on the costa, angled toward the base near the reniform spot, and concave toward the base and nearly perpendicular to the posterior margin below the spot. The subterminal line is light gray often widened to a whitish spot near the posterior margin, slightly irregular, and preceded by a gray shade that is strongest at both margins. The orbicular post is an upright or slightly tilted oval, outlined in black, filled with whitish gray peripherally and the ground color centrally. The reniform spot is moderate-sized, kidney-shaped, outlined in black medially and partially or entirely filled with light gray. The claviform spot is absent. The hindwing and fringe are light tan-gray, with darker ill-defined discal spot, postmedial line, and submarginal bands and a thin dark terminal line. The head and posterior thorax are powdery gray. The collar has a light tan base, a black transverse line, and a gray edge. The male antenna is bipectinate.

This species can be recognized by its small size, gray forewing color, short black basal dash, distinct pattern of dark lines and spot with lighter filling, and a tan base on the collar. It is most likely to be confused with Brachylomia sierra which is known currently from the Warner Mountains but might be more widespread in southern Oregon. Most of the pattern elements are similar in these species but the lines and spots are usually more distinct and lighter filled in B. obscurifascia. Males of these species can be definitively identified by brushing the scales from the tip of the valves and examining them under moderate magnification. The digitus of B. obscurifascia protrudes well beyond the ventral margin of the valve while that of B. sierra is short and is not visible from a lateral perspective.

The type locality of Brachylomia obscurifascia Troubridge and Lafontaine is Suplee, Crook County, Oregon, United States of America.

Habitat

This species occurs in moist forest or riparian habitats in the mountains of south-central Oregon.  It may prefer quaking aspen forests in this area. The type series was collected in an area with open pine forest-steppe mosaic.

Distribution

Pacific Northwest

Brachylomia obscurifascia is found in central and east-central Oregon.

Global

This species is only found in northeastern California outside of Oregon.

Life History

Larvae

No information is presently available regarding larval foodplants of this species, but it is probably a foodplant specialist feeding on willows (Salix spp.) and cottonwoods (Populus spp.) in the Salicaceae based upon related species.  It may prefer quaking aspen (P. tremuloides) based upon the habitat.

Adults

This moth flies during early fall. The type series and all examined specimens were collected in September. It is nocturnal and comes to lights.

Economic Importance

None.

Literature

 Lafontaine & Troubridge (2007)