Lambdina fiscellaria, the mournful thorn or hemlock looper, is a moth of the family Geometridae. It is found in North America, from the Pacific to the Atlantic coast and from Canada south to Pennsylvania, Wisconsin and California.

The wingspan is about 35 mm. The moth flies from August to early October depending on the location.

The larvae feed on hemlock, balsam fir, white spruce, oak and other hardwoods.

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