This week for Flora and Fauna Friday, it’s your local celebrity impersonator and the body-double of a beloved butterfly, the Viceroy (Limenitis archippus).
The Viceroy is a large butterfly found throughout the Eastern United States. The Viceroy’s wings are a burnt-orange crisscrossed with black veins, bordered with a heavy strip of black pinpricked by white, and with white spots at the wrist on the forewing. It’s a color pattern that is practically identical to that of the Monarch (Danaus plexippus). The only major visual differences between the two species are an extra black vein dividing the hindwing of the Viceroy, and the Monarch being a good third larger on average. Behaviorally, the two have a few telltale deviations. Monarchs rock and float more on the wing, whereas Viceroys often flutter in a straight line. Viceroys tend to stand atop vegetation while Monarchs dangle from it. But, at a glance when perched on a flower or gliding on the wing, the two look essentially indistinguishable. That’s by design. This is called Müllerian Mimicry. Both the Monarch and the Viceroy are toxic and foul-tasting to their predators. Thus they both benefit from bearing the same coat of arms and flashing the same warning signal to the world.
Unlike the Monarch, the Viceroy doesn’t migrate. They stay local to preferred habitats, generally wetlands, freshwater marshes, and river banks where Willows are plentiful. This makes their common name of “Viceroy”, a local ruler appointed by a wider ruling monarch, quite the apt name.
Viceroys, just like Monarchs, garner their toxicity as caterpillars by dining on their host plant. Here in the Lowcountry, Viceroys predominantly host on Willow trees (Salix spp.), eating their leaves and concentrating salycilic acid in their bodies. This is the same phytochemical that was studied and refined to create the medicine Aspirin. Viceroy caterpillars have a second defense mechanism as well and another form of mimicry. Their caterpillars have a lumpy greenish-brown body with a white saddle and two rugged black antennae. Their chrysalis has the same pattern as well, minus the antennae. Not only is this a fairly cryptic pattern that makes for good camouflage, but it also strongly resemble bird droppings. It might not be the most stylish appearance, but it certainly makes them an unappetizing target for avian predators.
