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The Big, Beautiful Two-Tailed Swallowtail
Arizona's's state insect is the two-tailed swallowtail butterfly. It was designated in 2001 and is one of many swallowtail species that are distributed across the United States, and around the world. This article tells you what you need to know about this wonderful butterfly.
The Two-Tailed Swallowtail Butterfly's Scientific Name
Arizona's state insect belongs to a group of butterflies that are distributed around the world, from chilly northern regions to steamy tropical zones. Northern species are some of the most familiar butterflies you will see, and include the tiger and black swallowtails -- these are big, beautiful, and often take nectar at flowers in the bright summer sun. The two-tailed swallowtail is one of the biggest butterflies in North America, and when you see one nectaring in the Arizona sun it leaves a lasting impression.
The scientific name for this group is the family Papilionidae. It There are many kinds of butterflies in the group, and they all share some special characteristics. The scientific name of the two-tailed swallowtail butterfly is Papilio multicaudata. That means the genus name is Papilio and the species name is multicaudata. Scientific names are always in italics.
Two-Tailed Swallowtail Showing its "Tails"
The scientific name of the two-tailed swallowtail indicates that it belongs to the genus Papilio, a large group of showy butterflies that often have tails on their wings. Early entomologists thought the tails resembled those of barn swallows, hence the common name. Papilio multicaudata is closely related to the widespread tiger swallowtail, as well as other yellow and black striped Papilio butterflies. It is limited in range to the southwestern United States, but will occasionally stray to central states, where it will typically not breed due to the cold temperatures of the winter months. The southern range of P. multicaudata extends all the way to Central America, where there are many, many Papilio species. Many of these tropical swallowtails are among the biggest and most beautiful butterflies in the world.
Two-Tailed Swallowtail Caterpillar
The larva of Papilio multicaudata resembles that of the tiger swallowtail, a related species that is widespread throughout the United States. It feeds on chokecherry, ash, and Arizona sycamore, all common trees in much of the state. Most are green, but they turn red or brown before pupating. Note the fake "snake's eyes" on the front sections. Interestingly, the size of the fake eyes is much less important than the shape. In other words, as long as the markings look like eyes, they don't need to be particularly large. Predators will be unlikely to take the chance, no matter how big the "eyes."
Another Swallowtail Species Showing Enormous Fake Eyes
Unusual Features of Swallowtail Caterpillars
Like all Papilio species, the caterpillar of the two-tailed swallowtail has some unique features and behaviors. Most interesting is something called an "osmeterium." It's located right behind the caterpillar's head, and consists of an orange, forked gland that the caterpillar can stick out whenever it feels threatened. The osmeterium looks a lot like a snake's tongue, and is designed to scare off predators like birds and frogs. It also smells bad, a little like rotten fruit. All things considered, it's a pretty great defensive tactic.
Another feature of many swallowtail caterpillars is large false eye-spots near the head. The caterpillar's real eyes are tiny; the big ones are only markings. But combined with the osmeterium, the caterpillar can put on a pretty good "snake show."
Finally, swallowtail caterpillars typically construct a kind of "seat belt" when they pupate. This is a band of silk that supports the chrysalis (pupa) on the stick or twig. No other group of butterflies does this!
The Osmeterium in Action
Yellow and Black: Universal Warning Colors
The bright yellow and black colors of the two-tailed swallowtail are almost certainly a defensive feature designed to warn away predators. Black and yellow, red, or orange are the colors of stinging and otherwise protected insects, a way to advertise to potential predators like birds and amphibians, "stay way! I sting!" Butterflies don't sting, of course, but they may obtain some protection by flashing warning colors to fool a random toad into thinking twice before it tries to make the butterfly its lunch.
"Complete metamorphosis" is the term used to describe the life cycle of insects that go through a four-stage sequence of forms. For butterflies, this means egg-larva-cocoon/chrysalis-adult. It helps to take the butterfly as the example, although dragonflies, bees, wasps, flies, beetles, and many other insects also go through complete metamorphosis. Like butterflies, they all have larvae and all of the other developmental stages.
The tiger swallowtail butterfly is typical of the insects that undergo complete metamorphosis. The egg is laid on a variety if leaves, and the caterpillar that hatches out eats the leaves of the plant. As it grows, it sheds its skin, also known as molting. The stages between molts are called instars, and after the last instar, the caterpillar sheds its skin one more time.
The last tine the caterpillar sheds its skin, it enters the cocoon/chrysalis phase, known by scientists as "diapause." It's also called a "pupa." Inside the pupa, the insect's cells are rearranging. They actually break down into a kind of goop, and then reassemble to form the body and wings of the adult butterfly or moth.
The final "instar" occurs when the insect hatches out of the pupal skin. It is now ready to mate and continue the cycle. The adult feeds just enough to promote the goal of mating and laying eggs; other than that, it has no purpose on this planet.
The following sources were used for this guide: