The Viceroy (Limenitis archippus) is a favorite amongst our staff and our audiences, and for good reason--it’s a pretty awesome caterpillar!
If you’ve seen a Viceroy caterpillar before, your first thought might have been, “Weird.” That reaction would be justified; Viceroys don’t look like typical caterpillars. In fact, they look like… bird droppings. I love speculating with kids over why Viceroys might look the way they do. If the kids struggle to come up with an idea, I ask them, “Would you want to eat food that looked like… your poop?” The answer has always been no, and for good biological reason—most creatures would really prefer to avoid eating their own poop!
With their clever coloration that mimics bird poop, Viceroys are attempting to avoid being eaten by birds. In order to be convincing bird droppings, however, Viceroys also need to BEHAVE a bit like bird droppings. Many species of caterpillars tend to hang out on the undersides of leaves. Being under a leaf is a good way to hide from predators and avoid drying out in the sun. But Viceroy caterpillars hang out on the TOPS of leaves, which is where it makes the most sense for bird poop to be. They’re right out in plain view there, but their bird poop disguise gives them some protection from being eaten.
On two of the attached pictures, you’ll see a whitish structure branching off to the right of the twigs. That’s a hibernaculum--an overwintering shelter. In late summer or fall, as temperatures begin to cool and leaves begin to die, early-instar Viceroy caterpillars build hibernacula. They wrap a leaf in silk, use silk to securely attach the leaf to its twig, and hunker down inside the leaf until springtime. When the first tiny leaves begin to emerge from their plant in spring, Viceroy caterpillars can immediately crawl out of their hibernacula and begin to feast on the spring foliage, which gives them a head start over other caterpillar species.
We’ve recently been finding our first Viceroys of the season—and you can, too! Search for willow, aspen, and poplar trees in meadows and along open edges of wet areas. If you find plants that are smaller and isolated from similar species, you’ll increase your odds of finding a Viceroy. See if you can find one on the top of a leaf, or an abandoned hibernaculum! Even if you don’t see a Viceroy, willow, aspen, and poplar are host plants for a wide variety of caterpillar species, so I’m confident you’ll find SOMETHING! Let us know what you see!
- Liz Kautz
TCL Education Director