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Cucullia intermedia is a medium-size (wingspan 4.5–5 cm) moth with uniformly medium to dark grey forewings, relatively unmarked except for numerous fine dark grey or black longitudinal lines. The normal spots are barely indicated by a faint partial outline of black scales. The hindwings are entirely grey-brown with the veins thinly lined with darker scales. The dark hindwings separate intermedia from all similar-sized Alberta Cucullia species. It is most likely to be confused with Cucullia speyeri, which is usually paler grey, has a small but prominent black streak in the anal angle of the forewing and mostly white hindwings. There are also significant differences in the genitalia of both sexes of the two species. Adults and genitalia of both sexes of intermedia are illustrated by Poole (1995).

The adults are nocturnal and come to light. There appears to be a single annual brood, with adults on the wing from mid May through early August, peaking in late May and early June. The larva is described by Poole (1995). Larvae have been reared from Lactuca biennis (Moesch.) Fernald and L. canadensis L. (Asteraceae). A large number were also collected from and reared on White birch (Betula) by the Forest Insect and Disease Survey, a most unusual host switch from the Composite herbs used by most species of Cucullia!

Cucullia intermedia occurs from Newfoundland to the coast of BC, south in the east through New England and in the west to CA and central AZ. It is common throughout most of Alberta south of the boreal forest, rare further north.