Ask The Entomologist, Community

Ask The Entomologist: Fluffy caterpillars

Last week I received an “Ask The Entomologist” identification request.
What is this fluffy caterpillar? It was found feeding on blackberry bush leaves.

First off, adorable. This is a Tussock Moth caterpillar, so called after the little clumps of hair on their backs. Many fluffy caterpillars are in this group, family Lymantriidae. This particular species is called the Spotted Tussock Moth, and is native to our region. It’s not a picky eater, and will gladly eat willow, birch, and a range of other deciduous trees. We have another related species in the area, the Douglas Fir Tussock Moth, which can become an awful lumber pest, and has been linked with some health conditions in forestry workers.

Beware! While Tussock Moths’ long hairs can feel soft if you stroke them gently, they often conceal shorter special defensive hairs! These “urticating” (itchy) hairs are like tiny spears and can be quite painful – some even come with venom. Many types of Tussock Moth urticating hairs can cause allergic reactions, the Spotted Tussock Moth (the one above) has even caused one case of anaphylactic shock. Even if you’re not allergic to the caterpillars, there’s the possibility of bacterial infection if the hairs break off beneath your skin.

Tussock moth caterpillars can prove even more dangerous if eaten! Whether by livestock (abortions in mares, presumably others as well), pets (tongue rot documented in dogs), or unattended toddlers (often surgery, no deaths reported yet…) . The most serious condition resulting is that the eaten caterpillars’ hairs can puncture the digestive tract. This may cause bacteria to seep from the intestines into the body cavity, and can cause serious illness. While a healthy organism may be able to survive this, it often proves fatal to unborn young, which don’t have sufficiently developed immune systems.

These caterpillars can be perfectly safe, and kids can have a great time watching them grow up into pretty little moths, but do be careful! If you think you, your kids, or your pets have been injured by contact with a caterpillar, Mayo Clinic has some medical advice. If you want to kill your Tussock Moth caterpillars, I suggest rubber gloves and a jar of soapy water.

Looking forward to more bug questions,


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