Milkweed tussock moth larvae feed on common milkweed

Milkweed is not just for monarch butterflies – milkweed tussock moths are also a frequent diner.

Colorful milkweed tussock moth larvae feeding. All photos: Patrick Voyle.
Colorful milkweed tussock moth larvae feeding. All photos: Patrick Voyle.

Common milkweed plants catch the spotlight as being the home and restaurant of monarch butterfly larvae, but that’s only part of the story. Right now across Michigan, other insects are finding common milkweed, Asclepias syriaca, a place of good food and good times.

The milkweed tussock moth, Euchaetes egle, begins its life as a tiny, nondescript larva, feeding with its siblings in a big herd. The ending its life as a larvae is an explosion of colorful tufts of hairs. Sometimes they are called milkweed tiger moths because the larvae are black, white and orange. The adult moths are not as colorful, being mainly a soft gray.

Life begins in June when mommy milkweed tussock moth lays her pale gray eggs on the bottoms of milkweed leaves by the dozens. The kiddies hatch out and begin eating the tissue off the bottom of the leaves. Kiddies are off-white and look slightly bristly or spikey with black, shiny head capsules. They feed as a crowd at this growth stage.

Moth larvae feeding.

Newly hatched milkweed tussock moth larvae feeding.

The caterpillars go through a number of instars or growth stages before becoming as large as they will grow as larvae. The little larvae strip the tissue off the leaves, but avoid the veins because there is a great deal of latex-like white sap that could glue them in place. Milkweed contains chemicals called cardiac glycosides that make the larvae poisonous and unattractive to predators, just as it does for monarch larvae.

Black tufts.

The black tufts are beginning.

Black tufts lengthening.

Black tufts lengthening and feeding on leaf.

As they grow, milkweed tussock moth larvae eventually feed on small veins, but large ones are untouched. Soon, the larvae have small, black dots on their light gray bodies and when viewed closely, the black dots are the beginnings of black tufts of hairs. As a leaf is eaten down to just a big midvein, it folds up and bends over to become a bridge or tightrope to a new leaf. Periodically, all the small larvae disappear for a day or so to molt into the next growth stage.

Leaf bridge.

Leaf bridge to another plant.

One day, after an absence, black, white and orange tufted larvae are wandering and feeding on the leaves individually or in pairs. They look like fuzzy bedroom slippers or little, calico-colored, fluffy shih tzu puppies. They no longer feed in groups. If there are other common milkweed in the vicinity, some of the brightly dressed larvae will move there. Soon, these larvae will leave the milkweeds and pupate in small, gray felted cocoons until next spring. It’s a journey of development worth watching.

Michigan State University Extension suggests if you have a garden in full sun, native milkweed is a good plant to include. It grows in full sun and can grow anywhere from 2-5 feet tall. If the plant has exceptional growing conditions, it could top out at over 6 feet. Then it needs to be staked because it is too tall for its own good. If you are giving native insects a feeding place, expect leaf damage will accompany the feeding. Flowers are incredibly fragrant and several plants in a clump can have dozens blooming at the same time. Be a smart gardener and give our native insects a table at your milkweed restaurant. 

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