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A medium-size (approx.3.5 cm wingspan) moth with clear light grey forewings and shining white hindwings. Forewing markings are highly variable, but often unmarked except for a thin black basal streak, thin black lines partially outlining the orbicular spot and filling the space between the orbicular and reniform, and some black streaking along the outer veins. Some specimens are much more extensively marked. Vocalis lacks the prominent rusty scaling characteristic of pallidicollis. Lafontaine states that females of the two species can by separated by the raised, sclerotized lip-like rim of the ostium bursa of vocalis. However I find this a less useful character than one would expect! A more useful character appears to be the size and shape of the bursa itself. In vocalis the small, clear round lower half of the bursa is well defined from the thick-walled upper half; in pallidicollis the lower chamber is larger and blends less perceptively into the upper half. Lafontaine (1998) illustrates the adults and genitalia of both sexes. There are a number of other moths, in particular several species of Xestia, which superficially look like vocalis.

A western species, distributed throughout much of the Great Basin and Rocky Mountains, east to central Montana, western South Dakota, Colorado, New Mexico and west Texas, west to Nevada and eastern California. The only Canadian record is from Waterton Lakes National Park, where it was found in open Douglas fir grasslands on a south facing slope at about 1350 m elevation.