SPECIES SPOTLIGHT: Battus philenor, the Pipevine Swallowtail

Welcome to part one of a series I am doing called Species Spotlight. Each entry will showcase one particular species of invertebrate, whether it’s a butterfly, a moth, an arachnid or a millipede. Wherever possible I will use my own photographs and each entry will feature general information of the species as well as any additional notes that I can add, based on working with said species. The topic of this entry is the Pipevine Swallowtail, Battus philenor. 

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Though most people are fully aware of the Monarch butterfly (Danaus plexippus), it’s usually the swallowtail butterflies (Papilionidae) that impress the most, not only for their large size but for their spectacular colors. There are approximately 550 species world-wide, with only a small representation in the United States. They get their names from that fact that most species have tails on their hind wings (these are thought to imitate antennae so that when birds go to eat a butterfly, they focus on biting the tails instead of the head, giving the butterfly a chance to escape). Probably the most common on the east coast is the Eastern Tiger Swallowtail (Papilio glaucus), known for its bright yellow and black markings.

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Growing up, I saw that the Pipevine Swallowtail was supposed to be common in my area, based on what I was reading in my very worn copy of the Golden Press Book “Butterflies and Moths: A Guide to the More Common American Species” by Robert T. Mitchell and Herbert S. Zim (review HERE). The problem was I never saw them (or heard reports of them). It wasn’t until many years later that I figured out why. More on that later.

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The butterfly itself is spectacular to look at, especially with freshly emerged individuals. The upper wings are dark but feature an iridescence that when sunlight hits it the right way it is comparable to the blue seen in many Morpho butterflies from South America, especially in the males! The markings on the under wings, especially with the hind wings, are comparable to what you would see in both the Spicebush Swallowtail (Papilio troilus) and the Eastern Black Swallowtail (Papilio polyxenes asterius), the only difference being that here the blue is very vibrant and metallic looking!

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Like all butterflies, Pipevine Swallowtails, go through a four-stage, complete metamorphosis (egg, caterpillar, chrysalis and adult). The eggs are rust colored and are laid singly and in groups. If the egg is laid on the tips of the young vines then usually just one or two eggs are laid at a time. If they are laid on the underside of a leaf, then a dozen or more can be left in one spot. They are relatively easy to find as their orange color is a strong contrast to the green of the Aristolochia vine, aka Dutchman’s Pipe, that they feed on. You would assume that this would also make it easier for predators to find them as well but thankfully the toxicity of the food plant is passed from the caterpillar to the chrysalises to the adult and then back to the egg. There seems to be no rhyme or reason as to where they lay in relation to the ground either as I have found eggs twenty plus feet in the air as well as just a few feet off of the ground.

The caterpillars are very interesting and remind me of those of the birdwing butterflies (Ornithoptera). They range is color from an almost black to red and the bodies are covered with nodules, giving them an other-worldly appearance.  The nodules are often a reddish color, contrasting to the dark coloration of the rest of the body. These could act as warning colors as their food plant is toxic, making them toxic as well. Along the sides of the body are fleshy filaments, with the two longest near the head. To me these look like legs and antennae, perhaps imitating a centipede. They will eat everything on the plant, from leaves, vines to seed pods. Raising them in captivity is extremely easy as long as you have a lot of fresh food and clean conditions.

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The chrysalis is typical of all swallowtail chrysalises. They are attached by a silk pad at the tip of the abdomen and then there is a silk girdle around the mid-section, creating a second attachment point to the plant. They can range in color from a yellowish-green to green to brown, depending on where the chrysalises are made. Those made on leaves tend to be lighter and those made on branches tend to be darker, helping to camouflage against predation. Interestingly enough though, I have had overwintering chrysalises that were green and yellow, meaning they would stick out pretty predominantly during the winter months. This may have to do though with rearing in captivity as opposed to what may happen in the wild. The color of the chrysalis does not affect the colors of the adult butterfly in any way.

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As mentioned above, this species is spectacular to look at. Even one that has been around for a while and has taken a beating, can still be stunningly beautiful. This butterfly is toxic, thanks to the food plant that the caterpillar fed on. Any predator that eats one of these will more than likely avoid them in the future. The spectacular metallic blue contrasting with the bright orange spots on the undersides of the hind wings provide great warning colors. The body also features a thicker than usual exoskeleton and glands that will emit an acrid liquid when pinched (like when a predator tries to bite down on them). Less damage is then done by the bite and the butterfly is able to survive.

One of the most interesting aspects of this butterfly is how many other species actually mimic it in appearance, to protect themselves from being eaten. In what is known as Batesian mimicry, other species imitate the colors and markings of a toxic or dangerous animal so that predators stay away from them, knowing that the species being imitated could hurt them. Three of the best examples are the Diana (Speyeria diana), the Spicebush Swallowtail (Papilio troilus) and the Red-spotted Purple (Limenitis arthemis astyanax). The dark female form of the Eastern Tiger Swallowtail also uses Batesian mimicry.

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The Pipevine Swallowtail can be found throughout a good part of the United States. Areas of the map labeled as strays are slowly becoming established, especially as northern temperatures get warmer. This species seems well established in my area with many individuals being seen annually, due to the fact that I have planted many large pipevine plants on my parents’ property. Living on an island makes it even more difficult for something like a butterfly to stray into, making me believe even more that they are now well established here.

The saying “if you build it, they will come” certainly applies to butterflies, in particular when it comes to butterfly gardening. If you just plant flowers, you will attract butterflies as they pass through your yard on the lookout for places to lay their eggs. If you provide those caterpillar host plants as well, they will stay in your yard much longer. I had this happen both with the Pipevine Swallowtail and the Giant Swallowtail (Papilio cresphontes). Both species that were never seen during my childhood are now common visitors, on a daily basis!

It’s nice to see an animal, that is so sensitive to its surroundings, especially in regards to global warming, thriving, especially on a small island. Providing their favorite plants and flowers is certainly a step in the right direction and by doing so, not only are you helping local species that need all of the help they can get, it also will provide you hours of enjoyment as these beautiful creatures become regular visitors to your home.

 

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