Wild Profile: Meet the tiger swallowtail butterfly

An eastern swallowtail butterfly feeding on a flower By Maria T Hoffman/Shutterstock

Nothing brings spring cheer like the sight of tiger swallowtail butterfly flitting about and fluttering its wings as it drinks nectar from its favourite plants. The tiger swallowtail isn’t quite as recognizable as the monarch or the luna moth, but it’s certainly eye-catching with its black-and-yellow markings. There are actually several North American species of these tiger-striped insects; the eastern tiger swallowtail is the most widespread.

Do male and female butterflies look different from each other? 

Everyone knows that the males and females of plenty of bird species have different plumage, and different body sizes, in some cases. Male and female butterflies have differences too. In some species, males have a thinner abdomen, for example, or differently-shaped forewings. But, in the southern reaches of their range, eastern tiger swallowtail females are, in many cases, nearly pitch black. Why? It’s likely an evolutionary adaptation. In areas of North America where the tiger swallowtail occupies the same habitat as the all-black pipevine swallowtail, this form of mimicry helps the lady tigers. Pipevine swallowtails taste nasty to bird predators, so a black outfit tricks birds into also avoiding any tiger swallowtails.

What does the tiger swallowtail eat? 

Along with nectar—which the butterfly identifies and samples using taste buds on its feet—butterflies drink the water from mud puddles. (This is why you might notice groups of them hanging around wet roadsides in the spring.) Males are especially fond of the salt they can suck up from the muddy side of the road. They need sodium, along with amino acids that they get from animal droppings and carcasses, to build up nutrients in their sperm capsules in time for mating. (The tiger swallowtail only produces one generation of offspring per year, so it has to count.)

What does a tiger swallowtail caterpillar look like? 

Tiger swallowtail babies aren’t pretty: they’re tiny and look like black-and-white bird droppings. As they get older, the caterpillars turn green, with yellow or orange black-dotted spots positioned behind their heads. This is another mimicry strategy. The spots look like eyes, which makes the caterpillar appear a little like a fat green snake. (At least to a predator.) But the caterpillars also have a defence strategy if an ant, spider, or parasitic wasp attacks. A tiny fork-shaped appendage springs out from behind the caterpillar’s head, and produces a gross smell to deter the potential predator. It must work—who would eat something attached to a stinky fork?

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