Pacific Northwest Moths

Identification

Adults

Euxoa emma is a small to medium-sized, cream-colored Euxoa (FW length 14–16 mm) that flies near the Columbia River in north-central Washington during early summer. The forewing is pale cream with black transverse lines dominated by the median line. Smoky gray suffusion is often present in the distal subterminal and terminal areas. The lines are dark black, single or partially double with strong and weak components, filled with the ground color. The basal and antemedial lines are thick on the costa, slightly irregular, angled slightly toward the outer margin. The median line is thick and diffuse, bent with the apex near the lower reniform spot with a characteristic laterally convex segment below the spot that is most prominent along the medial border. The postmedial line is usually simple, thick on the costa, finely toothed elsewhere, smoothly curved around the reniform spot and angled slightly toward the base below the spot. The subterminal line is the pale ground color, usually preceded by a dark spot on the costa and a diffuse gray shade across the mid-forewing. The terminal line is black, thickened between the veins. The fringe is pale gray-tan. The orbicular spot is oval, usually lacking a dark border but evident as slightly lighter filling or a central gray spot, occasionally absent. The reniform spot is also vague, most often evident as gray central filling. No claviform spot is present. The hindwing is slight tan off-white with a light gray marginal suffusion, slightly darker with a wider band in females, with slightly darker veins, discal spot, and terminal line. The fringe is white with a tan base. The head and thorax are cream without dark markings. The frons bears a flat-topped tubercle. The male antenna is bipectinate. Euxoa emma is a member of the large subgenus Euxoa.

Euxoa emma can be identified in its limited north-central Washingon range by its cream color, black lines with a cookie cutter concavity below the reniform spot, and near absence of forewing spots. It is similar in appearance to the closely related Euxoa annulipes which occurs as far north as east-central Oregon. Euxoa emma is lighter and warmer colored, lacking gray tones, and has more sharply-defined forewing markings than E. annulipes. These species also differ in characters of the valve of the male genitalia. In practice, they can be separated by locality since E. annulipes does not occurs in Washington. Euxoa lineifrons, found in eastern Idaho, resembles E. emma but is more closely related to Euxoa comosa. The median line of E. emma is darker and contrasts more with the pale whitish forewing color than that of E. lineifrons, and its hindwing is lighter colored in both sexes. These species are also allopatric and are therefore unlikely to be confused.

The type locality of Euxoa emma L. G. Crabo and A. Crabo is Washington, Ferry County, S of Jim Mt., 47.900°N 118.495°W, 2175'.

Habitat

This species is narrowly endemic to open dry ponderosa pine forest with metamorphic rock outcrops along the Columbia River in northeastern Washington.

Distribution

Pacific Northwest

Euxoa emma is only known from the type locality near the north shore of the Columbia River (Lake Roosevelt) in Ferry County, Washington. It might be more widely distributed along the Columbia River, possibly into British Columbia.

Global

This species is endemic to Washington State.

Life History

Larvae

No information is presently available regarding larval foodplants of this species, but it is probably a soil-surface feeding cutworm that feeds on herbaceous vegetation based on related species.

Adults

The adults of Euxoa emma have been collected in late June and early July. They are nocturnal and come to light.

Economic Importance

None.

Literature

Crabo A & Crabo L (2007)

Moth Photographers Group