The Mournful Thorn or Hemlock Looper (Lambdina fiscellaria) is a moth of the Geometridae family. 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 September depending on the location.

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

Subspecies

There are three recognised subspecies:

• Lambdina fiscellaria fiscellaria
• Lambdina fiscellaria lugubrosa
• Lambdina fiscellaria somniaria

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  Lambdina fiscellaria fiscellaria Caterpillar
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  Lambdina fiscellaria lugubrosa Caterpillar