Swallowtail Butterfly Natural History
The swallowtail butterfly is a name for a number of species of butterfly that fall under the family Papilionidae. There are over 550 different species of swallowtail and they exist on every continent except for Antarctica. These beautiful, colorful, and surprisingly durable insects have been observed living in even the coldest northern reaches of Siberia and in the high-altitude Himalayan mountains. The family includes the largest known grouping of butterflies in the world, the birdwing butterfly. Swallowtails are known for their large and brightly colored wings along with their characteristically forked hindwings.
Because they come in such a variety of colors, swallowtail butterflies are highly sought after by collectors. Common cultural depiction often use swallowtail butterflies to represent the grace and free nature of the ineffable human soul. Other concepts associated with swallowtail butterflies are hope, endurance, change, and life. They were first described by the Swedish biologist Carolus Linnaeus in the 18th century and are currently among the most well-known insects in the world. Several US states have designated species of swallowtail butterfly as the official state insect.
Appearance & Anatomy
Swallowtail butterflies are insects, and so like all insects have a 3-segmented body composed of a head, thorax, and abdomen. They have 2 antennae perched on the head that they use to probe and sense the environment and two large compound eyes. They lack functioning mandibles and so consume an all liquid-diet by using a long proboscis to drink the nectar and pollen out of fruit and flowers. Each of their six legs are covered in chemoreceptors which they use to detect food, predators, and other swallowtails in the environment. Swallowtail caterpillars have small cylindrical and stout bodies that are divided into multiple distinct, fleshy segments. Swallowtail caterpillars are distinguished from other caterpillars due to the presence of an osmeterium, a fleshy horn like organ that expands and emits a foul smelling chemical to deter predators. Swallowtail caterpillars are easily mistaken for monarch butterfly caterpillars, as both are a fleshy greenish color.
The most noticeable feature of swallowtails is their large colorful wings. Swallowtail wings come in a wide variety of colors, from white and yellow to blue and black. Wing color can vary greatly even within a species. Genes that control for melanin production can be easily switched on and off, resulting in multiple color pallets for a single species of swallowtail. Other species wings change color depending on the surrounding environment. The particular color is due to tiny scales that line the wings. Several species’ wings will have scales of more than one color arranged into complex shapes and patterns. Wing size varies greatly between species, with the dainty swallowtail butterfly having an average wingspan of only 2 inches long, to the massive Papilio cresphontes butterfly whose wingspan can reach up to 6 inches. Most species of swallowtail have hindwings that terminate in 2, 3, or 4 little tails that resemble the feathers of a swallow.
Several species of swallowtail use their color as a form of self defense. Swallowtail butterflies are often colored in such a way so that they appear as distasteful prey, thus preventing predation. This form of self defense is known as Batesian mimicry—when a harmless organism evolves to imitate the appearance of organisms harmful to predators directed at both. Predators see the coloring of the wings, believe the swallowtail to be some other organism that will make them sick, and so leave them alone. For example, the eastern tiger swallowtail (Papilio glaucus) has evolved to protect itself from predators by mimicking the poisonous pipevine swallowtail (Battus philenor). Learn more about insect camouflage.
Swallowtails are diurnal meaning they are primarily active during the day. They prefer warm temperate areas and dislike cold arid regions. Most species of swallowtail have a life expectancy just around 1 month. Some, like the black swallowtail (Papilio polyxenes) live only 10-12 days, while other species have been recorded living up to 45 days. Because their lifespan is relatively short, most of the time in a swallow tails life is spent looking for food and opportunities to reproduce.
Swallowtails enjoy different diets depending on their stage of development. Swallowtail caterpillars subsist on a diet of leaves and other vegetation that they chew up with their tiny jaws. Many species of swallowtail caterpillars eat mildly toxic plants and become toxic themselves, thus protecting them from predators. Swallowtail larvae have also been seen to feed on common garden crops like carrots, dill, parsley, and fennel. Because of this penchant for garden food, swallowtail caterpillars are considered agricultural pests in some regions. Swallowtail adults lack functioning mandibles so they cannot bite or chew food. Instead, they lap up nectar from fruit and flowers using a long proboscis with a spongy appendage affixed to the end. Adults will also sometimes feed on mud or animal manure.
Every swallowtail goes through 4 stages of development: egg, larva, pupa, and adult. After mating, females will lay their small dewdrop shaped eggs on the underside of leaves. The close proximity to the plant ensures that the hatched caterpillars will have an immediate source of food. Once hatched, the caterpillars set off on their own, looking for food. Once they have eaten enough, caterpillars will encase themselves in a cocoon of silk known as a chrysalis, where they will undergo metamorphosis into the final adult stage of their life. Most swallowtails take a few days to fully transform. Once the adult emerges, it flies out in the world looking for opportunities to mate and reproduce.
Swallowtail mating is a relatively unceremonious affair. Males will fly around releasing a chemical meant to attract females. Once finding a suitable mate, the two insects will copulate, after which the fertilized eggs are laid on the underside of the leaf. Parents have no involvement in the raising of larvae and they are left to fend for themselves. Male specimens of some species will actually produce a glue like substance to seal up the female genital opening to prevent further mating.