Pacific Northwest Moths

Identification

Adults

Euxoa perpolita is a medium-sized Euxoa (FW length 14–17 mm) that flies in dry conifer forests during late summer. Its forewing is very smooth, slightly shiny, and dark red-brown or brownish black with black outlines of the orbicular and reniform spots. The forewing is relatively short and broad with a slightly pointed apex and convex outer margin. The color is rich and even, waxy, and dark brick-red with darker brown-gray outer margin or completely brown-black. The orbicular and reniform spots are outlined in black and filled with the ground color. The orbicular spot is small and round and the reniform sot is moderate-sized and kidney-shaped. All other markings are lacking. The hindwing is tan-gray with a dark gray margin, dark veins, discal spot, and terminal line. The hindwing fringe is two-toned gray. The thorax usually matches the forewing color, although some reddish individuals have dark thoraxes. The frons bears a flat-topped tubercle. The male antenna is biserrate. Euxoa perpolita is placed in the subgenus Orosagrotis. This subgenus is characterized by the orientation of the male vesica which extends to the left from the aedeagus and the position of the ductus seminalis which joins the right side of the corpus bursae.

This species can be recognized by its waxy dark red or brown-black forewing with small black spots. Other dark red Euxoa species, such as Euxoa excogita, and black ones such as Euxoa punctigera, have light scales in the forewing spots and usually some other pattern elements. Abagrotis brunneipennis can have a similar satiny red-brown color and flies with E. perpolita at several locations. It lacks the black-outlined spots and usually has more prominent transverse lines than E. perpolita.

The type locality of the synonym Carneades exculta Smith is British Columbia.

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 amongst 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

The larva is unknown.

Habitat

This species is widely distributed across Canada in a variety of habitats.  In northeastern North America and on the Great Plains, it is typically found in dry sandy habitats.  However, in the northern Rocky Mountains and north Cascades, it occupies spruce-fir and pine forests. It is relatively sporadic and rarely collected in the Pacific Northwest.

Distribution

Pacific Northwest

Euxoa perpolita is limited to southern British Columbia, northern Washington, and northern Idaho in the Pacific Northwest.

Global

The range of this species extends across Canada to the East Coast where it is found from the island of Newfoundland to Massachusetts. The western range extends south to the western portions of Montana and South Dakota outside of our region.

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

Euxoa perpolita has been collected from early August to early September in the Northwest. It is nocturnal and comes to lights.

Economic Importance

None.

Literature

Lafontaine (1987)

Moth Photographers Group