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One of the most widespread and recognizable geometrid moths. The broad pinkish borders on a yellow ground colour make this mid-sized geometrid distinctive, although the intensity of the pink margins varies considerably. Females are slightly larger with coarser dark speckling in the wing margin

The unique larva of this species, as the name suggests, has two tongue-like lobes along its back, unlike any other looper. In addition, the colouration and texture is bark-like, making it an excellent twig mimic (see Ives & Wong 1988 and Wagner et al. 2003). Pupation is in a loose cocoon among foliage. The pupa is very glossy, reflecting the colours of its surroundings. The nocturnal adults, emerging in late summer, resemble yellowing or wilted leaves. Eggs are laid on twigs and in old alder catkins, and overwinter (McGuffin 1987).