Pacific Northwest Moths

Identification

Adults

Euxoa bochus is a distinctive, small to medium size moth (FW length 14–17mm) that flies east of the Cascade and Coast Range summits during summer and early fall. It has a finely speckled, light violet-gray forewing with a dark red-brown costa. In addition to these features of the forewing, the terminal area is dark gray-brown. The lines are dark gray, usually absent or incomplete. The median line is dark red-brown and the postmedial line is comprised of a series of black spots. The median line is a series of smaller spots. The fringe is gray with a tan base. The orbicular and claviform spots are absent, and the reniform spot is a blackish gray kidney-shaped spot. The hindwing is nearly white with a faint margin shade in females, and small dark discal spot, dots on the veins along the course of the postmedial line, and dark terminal line. The hindwing fringe is white. The head and thorax are gray with a very thick velvety bar across the collar. A frontal tubercle is present. The male antenna is weakly biserate. Euxoa bochus is the only member of the subgenus Crassivesica, considered to be a primitive lineage of the genus Euxoa (Lafontaine 2004).

This species can be recognized by the two-toned dark red-brown and light gray forewing with abundant black speckling, a postmedial line comprised of black spots, and very broad dark band across the base of the collar. It is unlikely to be confused with other moths in our area.

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.

Larvae

Larva is smooth, yellow-green with a pale dorsal band and darker brown subdorsal and lateral lines.  It is illustrated by Lafontaine (2004).

Habitat

This species is found in dry, coniferous forest habitats of western North America.  In the Pacific Northwest, it is moderately common in dry, open ponderosa pine forests and juniper woodlands at middle elevations east of the Cascades, and is usually rarer in dry sagebrush steppe at low elevations.  It is not uncommon in spruce-fir forests at higher elevations.

Distribution

Pacific Northwest

Euxoa bochus is found in the drier interior parts of the Pacific Northwest from south-central British Columbia south. An isolated record from west of the Cascades is shown for southern Vancouver Island by Lafontaine (2004), but the species has not been found elsewhere in the Gulf of Georgia region. It has been collected in northern and southeastern Idaho.

Global

This species occurs from south-central British Columbia and south-western Saskatchewan to northern New Mexico, central Utah, and south-western California.

Life History

Larvae

This species appears to be a generalist feeding on various herbaceous vegetation in such families as Fabaceae and Asteraceae, but may also feed on grasses (Poaceae).

Adults

Adults fly in late summer and fall. Pacific Northwest records are from late summer through September. It is nocturnal and comes to lights.

Economic Importance

None.

Literature

BugGuide

Lafontaine (1987)

Lafontaine (2004)

Moth Photographers Group