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A rather small, bright green geometrid with two white transverse lines. Synchlora aerata is similar, but the transverse lines are scalloped rather than smooth, and the abdomen has a white dorsal line, not round spots as in Nemoria. N. unitaria has the white hindwing PM line closer to the wing base (about halfway to the margin), while mimosaria has the line more than halfway from the wing base to the outer margin; the PM and AM are also often connected forming a U-shaped white line on the hindwing rather than two discrete lines which meet the anal margin. The other two Alberta Nemoria, rubrifrontaria and darwiniata, have more than one pink-ringed abdominal spot, mimosaria has at most one spot, never encircled in pink.

The unique larvae of Nemoria species bear lateral flanges, and those of mimosaria have toothed, forward pointing flanges resembling dead plant tissue such as willow catkins. The pupa overwinters (Wagner et al. 2001). Adults come to light.

Larvae feed on a wide variety of deciduous shrubs and trees, and also on conifer trees (McGuffin 1988). Prentice (1963) reports the largest proportion of larval collections from white birch (Betula papyrifera) and balsam fir ((Abies balsamifera).