Pacific Northwest Moths

Identification

Adults

Euxoa campestris is a dark purplish-brown, small to medium-sized Euxoa (FW length 14–17 mm) with black filling of the cell that flies in forests in the eastern part of our region and British Columbia during the summer. It has scattered, light yellow scales lining the forewing spots. The forewing is very dark brown with a purple tint. The costa and terminal area are slightly darker gray and in some specimens there is a slight red flush in the subterminal area and at the apex. The cell is black. The basal and antemedial lines are black, double with filling of the ground color or a lighter shade. The basal line is irregular, drawn to the base at the cell. The antemedial line is weakly zigzagged, nearly perpendicular to the posterior margin. The median line is dark gray, very faint. The postmedial line is single or double, weakly scalloped, drawn toward the base on the costa, weakly excurved near the reniform spot, and curved to meet the posterior margin at a right angle below the reniform spot. The subterminal line is very weak, comprised of powdery pale yellow spots, slightly uneven, preceded by a blackish shade. The terminal line is black, thin or a series of small spots. The fringe is concolorous with the terminal area, sometimes slightly redder. The orbicular and reniform spots are partially outlined by black, lined by powdery light yellow, and filled with the ground color or dark red-brown. The orbicular spot is round to elliptical, often open toward the costa or both anteriorly and posteriorly. The reniform spot is similar, also often open at one or both ends. The claviform spot is black, moderate-sized. The hindwing is gray, darker toward the margin, with darker discal spot, veins, and terminal line. The hindwing fringe is white with an ochre and gray base. The head and thorax are the same color as the forewing, with a thin black transverse line across the mid-collar and an orange central thorax. A frontal tubercle is present. The male antenna is strongly biserrate.  Euxoa campestris is a member of the declarata species-group of the subgenus Euxoa.

Euxoa campestris resembles our two other species in the same species group, Euxoa rockburnei and Euxoa declarata. Both have similar forewing color and pattern. Euxoa campestris is most similar to E. rockburnei, but can usually be identified by its darker color, slight red tint in the forewing spots and subterminal area, brighter orange central thorax, and slightly smaller size (14–17 mm versus 16–19 mm). The males can be distinguished by the relative lengths of the sacculus, saccular extension, and harpe of the right valve. In E. campestris the sacculus is similar to the saccular extension, and the latter is significantly longer than the harpe (Lafontaine 1987). Euxoa infracta is a fairly common and widespread species in the Northwest that resembles E. campestris in color. It tends to be smaller and has a more banded forewing with lighter copper-brown antemedial and subterminal areas, and lacks the black filling of the cell that is characteristic of E. campestris.

Euxoa is a very large genus with many similar species, many of which are also quite variable. The genus is defined by a saccular extension of the valves in males and sclerotized plates on the dorsal and ventral ductus bursae in females. The genus was revised by Lafontaine (1987) in the Moths of North America series and is divided into eight subgenera based on structural characters. These moths are among the most difficult to identify. Even though the forewing color and strength of various markings can vary significantly in some of the species, the shape of the lines and spots and the color of the hindwings (often different in the sexes) are more constant. The habitat and flight period are also important in helping to narrow the possibilities.

Habitat

This species is widely distributed in moist spruce-fir or mixed hardwood-conifer forests across Canada, extending southward throughout the Rocky Mountains.  In the Pacific Northwest, it appears to be rare and sporadic in coniferous forests of the northern Rocky Mountain region and in the mountains of British Columbia.

Distribution

Pacific Northwest

Euxoa campestris is found in forests in the eastern part of the Northwest. Records extend as far west as north-eastern Washington and the Blue Mountains of northeastern Oregon. It is most widespread in British Columbia where it has been collected across the central and southern province.

Global

This species is widely distributed in North America. The range extends from Alaska to the Atlantic Coast across boreal Canada. In the East the southern limit is northern New England, although a disjunct population is found in eastern Kentucky. The western population extends south to Utah, Arizona, and New Mexico in the Rocky Mountains. This species is replaced by Euxoa rockburnei further west.

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 upon related species.

Adults

Adults fly in late summer from late July to early September. They are nocturnal and come to lights.

Economic Importance

None.

Literature

Lafontaine (1987)

Moth Photographers Group