Pacific Northwest Moths

Identification

Adults

Mniotype ducta is a medium-sized to large moth (FW length 16–22 mm) that flies in forests east of the Cascade summit during the summer. It has a dark, brownish-gray forewing and a nondescript pattern that includes a black median bar, light gray filling of the orbicular and reniform spots, and a light subterminal line with a "W" mark. It is dull brown-gray, sometimes blackish, slightly darker in the median and terminal areas. The subterminal area is slightly lighter opposite the end of the cell and pale gray at the fold and posterior margin. A short black basal dash is thickest near the end. A black bar extends across the median area in the fold. The basal and antemedial lines are black filled with the ground color, toothed toward the base on the veins. The antemedial line is slightly excurved. The median line is black, faint. The postmedial line is black, strongly toothed on the veins, drawn toward the base on the costa, narrowly curved around the anterior cell, and then strongly angled toward the base below the reniform spot and curved toward the posterior margin through the fold so that the median area is much narrower posteriorly than anteriorly. The subterminal line is pale gray, thin, irregular and often broken into spots, offset below the apex and forming a moderate W-mark to the margin on M3 and CuA1. It is preceded by a dark gray shade posterior to the cell and a series black chevrons near the W-mark. The terminal line is a series of black triangles. The fringe is striped dark brown-gray with crossing light lines at the ends of the veins. All three spots are outlined by thin black lines. The orbicular spot is moderate-sized, round or oval, filled with light gray and a weak central ocellus. The reniform spot is moderate-sized, broadly kidney-shaped, filled with brown-gray medially and light gray elsewhere. The claviform spot is moderately large, fused to the median bar. The hindwing is whitish gray, with darker gray postmedial and marginal bands, discal spot, veins, and terminal line. The hindwing fringe is white with a gray and ochre base. The head and thorax are dark brown-gray with thin dark line across the distal collar. The male antenna is biserrate.

This species, like Mniotype tenera, is fairly nondescript in appearance. It can usually be recognized by its brown-gray color with a strong median bar, light filling of the orbicular and reniform spots, and pale subterminal line with a W-mark in combination with whitish base to the hindwing. It is most likely to be confused with M. tenera and Mniotype pallescens. Mniotype tenera is a browner moth. It has less pale gray in the forewing spots and subterminal area, and a darker hindwing. Its distal forewing is slightly rounder. Unfortunately, they only reliably separated by dissection - the male valves are depicted by Forbes (1954). Mniotype pallescens is more contrasting gray and light gray than M. ducta and has a white hindwing with powdery lines and bands. Apamea longula is similar in size and general pattern to M. ducta and flies with it at high elevations. It is a paler and browner moth. A short black line is present on its basal posterior margin that is lacking in M. ducta.

Habitat

This species is widely distributed in spruce-fir and montane forests across Canada and in the mountains of western North America.  In the Pacific Northwest, it appears to be narrowly restricted to this habitat in the Rocky Mountain region and in the Cascades.  It is often common at high elevations in the spruce-fir forests along the summit of the Cascades.

Distribution

Pacific Northwest

Mniotype ducta is found in the mountains of southern British Columbia and in the Cascades south through Oregon. It also occurs in northern Idaho and in the Blue Mountains of Washington and Oregon.

Global

This species is widespread in boreal forests of Canada and the northeastern United States as far south as New England and northern New York. It also occurs in the Sierra Nevada and Rocky Mountains.

Life History

Larvae

This species is known to feed on cherries (Prunus spp.) in the Rosaceae, but probably feeds on many hardwoods such as alders (Alnus spp.) in the Betulaceae and willows (Salix spp.) in the Salicaceae.

Adults

This moth flies during the summer from late June through August. It is nocturnal and comes to lights.

Economic Importance

None.

Literature

Moth Photographers Group

Powell & Opler (2009)