Pacific Northwest Moths

Identification

Adults

Euxoa pestula is an uncommon mottled dull gray brown medium-size (FW length 15-18 mm) Euxoa that barely enters the Pacific Northwest in western Montana and flies during summer. The forewing is relatively narrow for the genus. It is lightly mottled gray-brown, lightest in the subterminal area with darker mottling in the cell in the medial area, preceding the subterminal line, and in the terminal area. The veins on the posterior and distal wing are dark. The basal, antemedial, and postmedial lines are double, dark gray to black with filling slightly lighter than the ground. The basal and antemedial lines are irregular. The postmedial line is scalloped weakly, gently excurved with apex at the end of the cell. The subterminal line is pale, slightly irregular with a weak W-mark on the mid-wing; it is preceded by a dark spot on the costa and a series of indistinct dark wedges on the mid-wing. The terminal line is a series of dark lines between veins. The claviform spot is small, black, filled with the ground. The orbicular and reniform spots are similar, prominent compared to other forewing markings, with thin black lined by even-thickness pale scales and darker brown centers, darkest at the inferior reniform spot. The orbicular spot is round and the reniform spot is weakly kidney shaped. The hindwing is pale gray with darker veins, indistinct discal spot, and broad ill-defined marginal band. The hindwing fringe is white with a yellow and gray base. The head and thorax match the forewing color, with weak striation on the prothoracic collar. The male antenna is biserrate.

This species is one of a fairly large number of nondescript brown Euxoa species. It is most similar to Euxoa pleuritica, both in size and pattern, but also resembles Euxoa simona (a larger species), brown forms of Euxoa tessellata, Euxoa aberrans, and Euxoa septentrionalis. Euxoa simona is very similar but usually larger than E. pestula (simona FW length > 17 mm). Euxoa pleuritica is also closely similar, but its forewing pattern is less uniform and typically has coppery areas that are lacking in E. pestula. Euxoa septentrionalis is also strikingly similar in pattern, but it flies slightly later in the year, typically during fall, and is also a larger moth. All of these species are best diagnosed by genitalic dissection. The saccular extensions, a diagnostic feature of all Euxoa species, have flattened tips and are shorter in E. pestula than in E. pleuritica. This difference can sometimes be observed in dried mounted specimens without dissection if the valves are sufficiently exposed.

Larvae

Habitat

This moth is predominantly found in steppe or sparse forest habitats.

Distribution

Pacific Northwest

This is a Great Plains species that barely enters our region in western Montana. 

Global

Euxoa pestula is found in the Great Plains region of central North America. Most records are from the western plains near the Rocky Mountains from Alberta to Colorado, with scattered records from farther east. The species account on the Strickland Museum (University of Alberta) website notes that this species is uncommon in Alberta.

Life History

Larvae

The larva is a cutworm that feeds on a variety of low plants.

Adults

Adults fly during summer, from mid-June to late August. They are nocturnal and are attracted to light.

Economic Importance

None.

Literature

Lafontaine JD. 1987. Noctuoidea: Noctuidae (part) in Dominick RB et al., The Moths of North America North of Mexico, fasc. 27.2. 237 pp.

Moth Photographers Group