|THE METROPOLITAN NATURALIST
|Milkweed Tussock Moth (Euchaetes egle)
The Milkweed Tussock Moth caterpillar is found, sometimes in large numbers, on Milkweed (Asclepias spp.) plants
or occasionally on Dogbane (Apocynum spp.), where they strip the leaves leaving behind the larger veins. The
orange, white, and black haired caterpillar starts life as a nondescript hairy grey caterpillar, developing into the
colorful tufted insect seen here. These caterpillars will form a grey cocoon in which they transform into a moth with
grey wings and an orange and black abdomen.
The orange, white and black colors of the caterpillar and the yellow or orange and black adult moth (not shown
here) might be a warning to birds and other predators that the caterpillar accumulates toxic cardiac glycosides.
Cardiac glycosides are chemicals that affect heart contraction and heart rate. Many plants, including milkweeds,
produce these chemicals as a defense against animals that might eat them. The cardiac glycosides
accumulated by the caterpillar are retained by the adult moth, giving the moth some protection against
predators such as bats and birds.