The Hemlock Looper is a pale yellowish geometrid moth that can cause devastating defoliation to hemlock trees during population irruptions in boreal forests. Outbreaks occur periodically and can kill vast expanses of hemlock and balsam fir, dramatically altering forest structure. The inchworm caterpillar is pale greenish-yellow and hard to spot among needles.
Best time to see a Hemlock Looper
The best time to see a Hemlock Looper is August–September, when about 88% of U.S. sightings happen, based on 4,267 research-grade iNaturalist observations.
Not certain it is a Hemlock Looper? What bug is this? walks through what to check first and the lookalikes that catch people out.
Recent Hemlock Looper sightings near you
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