Forest Tent Caterpillar invasion in Canada

Subject: Caterpillar Infestation
Location: Regina, SK, Canada
July 4, 2014 11:04 am
I thought you might enjoy these pictures of a caterpillar infestation on tree trunks in Regina, SK, Canada. I was told by a local that they call these canker worms. There were about 10 trees all in a row and every tree trunk had these caterpillars on them in these large groups. Interestingly, I didn’t see a lot of foliage damage on the trees themselves, so I was wondering if they were somehow feeding on sap? The photos were taken in June. Thanks for your website. I love it.
Signature: Steven Sluder

Eastern Tent Caterpillars
Forest Tent Caterpillars

Hi Steven,
In May, we posted a letter with images from Maryland of a large aggregation of Eastern Tent Caterpillars,
Malacosoma americana, and they do feed on leaves.  According to BugGuide:  “larvae feed on leaves of many trees and shrubs but particularly members of the rose family such as apple, cherry, and crabapple.”

Correction:  April 16, 2016
These are actually closely related Forest Tent Caterpillars,
Malacosoma disstria, not Eastern Tent Caterpillars.  According to BugGuide, the caterpillars of the two species can be distinguished because “Eastern Tent Caterpillar (Malacosoma americanum) has an unbroken cream/white line along its back, and a dark face” while the caterpillar of the Forest Caterpillar is “dark-gray to brownish-black background body color, highlighted by broad, pale-blue lines and thin, broken yellow lines extending along each side; dorsum of each abdominal segment has distinct whitish keyhole or shoeprint-shaped marking; body has fine, whitish, and sparsely distributed hairs.”

Eastern Tent Caterpillars
Forest Tent Caterpillars
Eastern Tent Caterpillars
Forest Tent Caterpillars



1 thought on “Forest Tent Caterpillar invasion in Canada”

  1. Yah they sure are quit the bug. Army cartipilar is what we called them. I’m in Moose jaw Sask now, but that was quit a while ago when I lived in North bay Ontario Canada and I was trying to remember the exact year but I can’t. I was wondering if you could tell me the year that we had that infestation Please and Thank-you Karen


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