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Saturday - January 23, 2016

From: Winchendon, MA
Region: Northeast
Topic: Pests, Herbs/Forbs, Wildflowers
Title: Caterpillars on Milkweed in MA
Answered by: Anne Van Nest

QUESTION:

I have found every year a black/red caterpillars on my milkweed. They eat everything! I have never been able to find out what they are or how to get rid of them.

ANSWER:

The milkweed tussock caterpillar (Euchaetes egle) is a common summertime feeder on milkweeds (Asclepias spp.) and dogbane (Apocynum spp.) in a huge area from southern Canada to Texas. Wikipedia says that the older caterpillars are gregarious and sport tufts of black, white and orange hairs with a black head. This coloration mimics the monarch butterfly caterpillar in a hope to ward off predators. The adult butterfly is a gray and yellow with rows of black dots on the dorsum.

Willow House Chronicles has a blog post about your caterpillar. Barefootheart says: The Tussock moth label is a misnomer, as these moths are classified with tiger moths. Another tiger moth caterpillar that you are probably familiar with is the Woolly Bear.

Some people have an allergic reaction, developing a rash, after handling these caterpillars, so it is not a good idea to pick them up, no matter how cute and fuzzy them may look.

Female moths lay large batches of eggs, and while the caterpillars are tiny, they live together on one plant before dispersing. Monarch butterflies are well know to also use milkweed as their larval food source, but Wagner notes that Monarchs tend to prefer young shoots, while Tussocks are content to eat older foliage. The caterpillar will overwinter in a cocoon and emerge as a moth next year.

These caterpillars will most likely be an annual visitor to your milkweeds and a sustainable strategy should be to encourage more milkweeds fluorish so that there is plenty of host plants for you and your visiting insects.