The Western Tent Caterpillar, Malacosoma californicum pluviale

Tent caterpillars use tents to control their temperature. We found that they also modify the size of their foraging groups for the same reason.

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The caterpillars can suffer if temperatures get too cold or hot, and they use the tents to control their exposure to these extremes.

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In the mornings, or on particularly cold days, caterpillars orient themselves on the side of the tent facing the sun, where the incoming solar radiation raises their body temperatures.

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Caterpillars cool off in the afternoon. The tent provides shade at particularly hot times of the day.

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Caterpillars leave the tent together to forage, often arranging themselves in groups on leaves.

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Large colonies can completely defoliate their host, in this case, a hawthorn.

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The trees recover and grow new leaves quickly after the larvae move off the host to pupate.

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Thermal images show the benefit of tent caterpillars’ grouping behavior

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We tested our observations about caterpillar temperatures and group size.

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A red-backed jumping spider drags a 5th instar larva away for a snack.

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A 5th instar larva wears a white egg from a tachinid fly, a common parasitoid of caterpillars.

Posted on 8/8/2019 by Beau Larkin

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About MPG North

Established in 2005, the property boundary at MPG North encloses 200 undeveloped acres in Western Montana’s Swan Valley. Researchers and field staff manage the property to improve habitat quality for wildlife, discover new ways to restore damaged landscapes and study forest ecology. We also create opportunities to share what we've learned with local conservation organizations, students of all ages, management agencies and volunteers. Through these education and outreach efforts, we seek to inspire others to work together and protect undeveloped landscapes.