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Medium-size (3.0 – 3.7 cm wingspan) moths with moderately pointed forewings. Mildly sexually dimorphic, with males brown and females red-brown or pink. Forewings pale brown (males) or pink (females), crossed by a narrow slightly curved darker median band. The antemedian and postmedian lines and to a lesser degree the terminal line marked by a series of dark dots or spots where they cross the veins. Hindwings paler, almost white, with a dark discal dot and the postmedian line marked by a series of dots at the veins. Both wings lightly dusted with darker scales.

Adults are nocturnal and come to light. In BC two broods, likely only one in AB. Larvae are innocuous solitary defoliators. They are described by McGuffin (op cit.), and illustrated in color by Duncan (2006). They overwinter as pupae buried in the soil (Duncan, op. cit.).

The primary larval host in Canada is western hemlock (Tsuga), but it also feeds on Douglas fir (Pseudotsuga), Red cedar (Thuja) and firs (Abies), with fewer records from willow (Salix) and alder (Alnus) and other conifers (Prentice, 1963; McGuffin, 1987).

There are three species in the genus Thallophaga, one of which reaches Alberta. It was added to the Alberta list in 2003 by Ted Pike, who collected it at Window Mountain Lake in the Crowsnest Pass area. The pinned male illustrated above is from the Moths of Canada website; the live female is courtesy of John Davis.