Spicebush Swallowtail (Papilio troilus)

This week is the first week of truly summer-like weather we’ve had here in Ontario, with temperatures reaching 30ºC, and a few nice thunderstorms. It made me think of sitting in a park, reading a book with my dogs while butterflies gambol around me. Which then reminded me that blogging about a butterfly would be perfect for the season, so today’s post is going to be about butterflies!

Specifically, we’re going to focus on the spicebush swallowtail butterfly, a butterfly I’ve probably seen around here but didn’t recognize. Spicebush swallowtails are found in the eastern part of North America, ranging from southern Canada to Florida, and as far west as Oklahoma. They can be seen in a lot of different habitats, but mainly prefer to hang around the shaded edges of woods, probably so they can lure unsuspecting passersby into spooky forests.

Spicebush_Swallowtail_in_August

What a pretty flutterby! Image credit: Haar Fager via Wikipedia 

Spicebush swallowtails aren’t the flashiest of butterflies, but have a certain dark charm to them. They are mainly black, with rows of white spots on the edges of the wings, and blue on the base of the hind wings. They also have a pair of orange spots at the base of each wing, for a little extra panache.

When they are looking for food or mates, adult swallowtails tend to form large groups, in a behaviour known as ‘puddling’. Males preform elaborate courtship displays to get the attention of female butterflies, and both sexes will mate with multiple partners. Females are very particular about where they lay their eggs. To test out whether a leaf is a good spot or not, females will drum their legs on the leaf, as they have special sensors in their legs that can detect the chemical composition of the leaf. How cool is that?

Upon hatching, spicebush larvae immediately get to work. Their first priority is to make a shelter, which they do by eating certain parts of the leaf and then attaching silk to the midrib of the leaf. When the silk dries, it contracts, making a tent-like structure. The caterpillars stay in their tents during the day, emerging at night to feed.

Spicebush butterflies might but pretty, but the real stunners are the spicebush caterpillars, though they are a little terrifying to look at. Their main defence against predators is mimicry, though what they mimic depends on their life stage. When they first hatch, spicebush caterpillars look like bird droppings, so most animals leave them alone.

Spicebush_Swallowtail_Papilio_troilus_Caterpillar_2400px

This is the second stage of mimicry. Can you guess what it’s supposed to be? Image credit: Derek Ramsey via Wikipedia

As they get bigger though, they shed this disguise and adopt a more ambitious one. They turn green and develop spots on their heads to mimic eyes, looking like common green snakes. The ruse is completed with a fake snake tongue, which is actually an osmeterium that the caterpillars can extend when threatened. Mimicry in spicebush swallowtails doesn’t stop after metamorphosis; the adults resemble pipeline swallowtails, which taste nasty, which means most animals avoid them.

I’ve always been a big fan of butterflies; what’s not to like about beautiful little creatures flying harmlessly through the air? Still I think the spicebush swallowtail is one of the more amazing ones out there — mimics are always cool, so butterfly mimics are just the best.

Cover image source: Michael Hodge via Wikipedia

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