This week's featured butterfly is another large, dark-winged, red-bodied swallowtail. Often considered to be of Chinese origin, Byasa polyeuctes is thought to be the most common swallowtail in India and is found in the rest of Asia as far west as Iran. It becomes less common toward the west side of its range; it's rare in India's western states and, according to Vu Van Lien, in Vietnam. It appears on checklists for nature lovers even in countries like Iran where it's only an occasional visitor, and is madly popular on photo sites. Pinterest uses it as "related content" to attract traffic to pages that aren't really even about butterflies or about Asia at all.
Photo donated to Wikipedia By Abdullah Imran (Pakistan) - Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=93999237 .
This whole family of butterflies are sometimes called Batwings.
Sunny Chir's photo shows why. A bat has two big wings, and when it flies the legs and body may or may not trail behind. The Atrophaneuras have two big fore wings and long trailing hind wings. Both pairs of wings are used in flight, but they move more independently than many butterflies' wings can do.
The species has been through several changes of name. Old sources still call it Papilio lama. P. lama was then determined to be the same animal as Papilio polyeuctes, which was later reclassified as Atrophaneura and most recently as Byasa polyeuctes. Tros was also considered, and rejected, as a genus name. The genus name Byasa honors an Englishman whose name was Byas, and sounds like the words "bias a." In the tradition of naming the red-bodied swallowtails after characters in literature associated with funerals, a lama is a priest, and St. Polyeuctes is believed to have been the first Christian martyr in Armenia. Though real, Polyeuctes was the subject of a play by Pierre Corneille. How he pronounced his name is not positively known; like other Christian saints' names, "Polyeuctes" is pronounced and spelled differently in different countries, usually "Polly uke tees" in English.
In its wide range, polyeuctes was also "discovered" and "named" Papilio philoxenus. The name Philoxenus (Philoxenos, Philoxena, Philoxene), which means "friend to strangers" or a rich man who could afford to be hospitable, expressed many ancient Greek parents' hopes for their children's futures and is the name of several minor figures in Greek history. Several were remembered for their creative work but Philoxenus of Leucas was remembered for his gluttony. Though probably not morally responsible for the deadly sin of gluttony, large caterpillars do eat a lot, and polyeuctes are a large species. Philoxenus and lama are now considered subspecies of polyeuctes and there is a fourth subspecies, in addition to B. polyeuctes polyeuctes as "nominate" subspecies, called B. polyeuctes termessus. Some authors recognize additional subspecies.
With a typical length of 11 to 14 cm, about 4.5 to 6 inches, polyeuctes catch the eye by being large. Females tend to be slightly larger than males, but not so much as to make it easy to see whether an individual is male or female. They have a typical Atrophaneura color scheme--black, or faded black, with a pattern of red and white spots on the hind wings. These patterns identify the many species of Atrophaneuras. (Considering them in alphabetical order, we have ten more left to study.) Instead of having the white patch at the inside edge of the hind wing, polyeuctes has it near the outside edge. The red color can be a faded pink, as shown below, but is observable on the head and tail--in both senses of the word; polyeuctes have both red patches at the end of the body and red tips on the swallowtails on their wings.
Hard to see on living butterflies, but sometimes very conspicuous on museum specimens, are the male butterflies' scent folds. Most butterflies get by with small scent patches somewhere on the wings or body but male Atrophaneuras have deep folds of skin covered with hairs, not scales, at the inner edge of the hind wings. Relative to the size of the animal, a lot of polyeuctes' skin surface is used to release the butterfly's species-specific scent. Perhaps unfortunately for polyeuctes, their scent is not one of the sweet fruity or flowery ones that humans tend to find pleasant.
This male from Thailand might have been described as a real stinker, while living.
They fly high, getting most of their food from flowering trees, and are often recognized more by their shape than by their colors. They're often seen backlighted, as in this photo by Tandin Wangchuk from Bhutan.
They are most easily photographed when they come down to earth to sip water from puddles and stream banks.
The red or pink color is often brighter on the underside, as on this colorful specimen photographed by Antonio Giudici.
While drinking they can be said to have "the common touch." While some of the Atrophaneuras are strictly pollinators, polyeuctes are also composters. Or at least the males are. In many swallowtail species, females are normally pollinators, drinking only flower nectar, because they get the mineral salts they need from contact with their mates--males are primarily composters. Apparently females don't like the bitter or salty taste of the minerals their bodies require. Possibly the way they absorb these chemicals even affects their eggs in some way. They need minerals but visit the spicier places where the males gather only if unable to find a mate. Male polyeuctes gather at puddles and also sip liquids from decaying carrion.
In this video, set to music by Yuichiro Manabe, two polyeuctes politely ignore their drinking buddy, the black-bodied swallowtail, who seems to want to quarrel, until he goes away!
This pair in Taiwan aren't ignoring each other, nor are they fighting. They are probably courting.
The polyeuctes at the top of the page here seems to be one of a mixed group of big showy butterflies that drink together in a park. Other lifeforms appear below the butterfly photos.
They are most numerous at relatively low elevations, but can survive high up in the Himalayas, too. Since their caterpillars' primary food plant is vines in--can you guess?--the genus Aristolochia, and the adult butterflies like nectar from tree blossoms, they are most often found in or near forests. (Some sources claim that they can also eat pitcher-plants, but the most reliable sources don't mention this.)
Photo from Ondrej Zicha at biolib.cz.
They're called Windmills because the wings can be spread out into an X shape in a museum's display case, but they do have a special way of flying that makes them easy to recognize from below. Polyeuctes have longer, thinner wings than most butterflies; like other Atrophaneuras they tend to fly slowly, sometimes moving the fore and hind wings separately, and may seem to "dive" or "crash" when they alight. While eating they can keep fanning their fore wings into a blur above their outspread hind wings, on which the two big white dots above a faint half-ring of reddish dots probably suggest a larger bird-eating animal to hungry but wary birds.
If a bird were so reckless as to ignore the warning, the butterflies get their colors from Aristolochia, a vine genus sometimes called birthwort. Extracts of the vines were used as a medication in difficult childbirths because the human body rejects them vigorously, sometimes vigorously enough to push the baby out into the world. Most warm-blooded animals reject all the Aristolochias and phytochemicals extracted from them. If a predator who eats an Atrophaneura butterfly can vomit, it will. If it can't, it will probably spend a day or so wishing it could. Birds that have even tasted and spat out one polyeuctes will thereafter avoid anything that looks as if it might be another polyeuctes, a fact that clearly benefits several other butterflies.
In some of their territory Byasa polyeuctes are mimicked by other butterflies and by some moths; they have "Batesian" mimics (animals that are not especially distasteful to birds, but benefit from birds thinking they would be) and "Mullerian" mimics (animals that are toxic or distasteful to birds in a different way). Here's an article describing some of this mimicry in detail, with pictures.
See also Minoru Tanaka's Spectrum of Sex, a wonderfully dry, technical book about the DNA sequences that allow only females of a species to benefit from mimicry while males don't seem to be mimicking another species.
The biochemicals that make butterflies inedible may turn out to be useful to humans. Byasa polyeuctes termessus (or termessa) contain a toxic chemical called papilistatin. Some researchers think that, if it could be applied in the right way, papilistatin might be used to stop cancer cell growth or kill germs. Doctors aren't rearing Common Windmills as sources of medicine yet, but who knows whether some day they will.
Is that why B. polyeuctes termessus inspired the composition of a piece of orchestral music?
Probably all butterflies use scent as a primary means of communication, but their odors usually are not noticed by humans, or, if noticed at all, are described as sweet and fruity or musky. The odors emitted when swallowtail caterpillars' osmeteria pop out generally remind people of pineapple, bananas, or other tropical fruit. Polyeuctes is one of very few butterflies that humans ever notice as having a "foul odour" when it's not under any special stress, though some other butterflies release enough scent that humans can agree they smell bitter or acrid when crushed.
While some Atrophaneuras maintain their "rare" status by having only one generation per year, polyeuctes reproduce continuously from April to September. This helps make them "common." Each individual butterfly flies for about two weeks.
This species' life cycle has been very scantly documented online. While photos of adult butterflies are abundant, photos of earlier stages in their lives are almost nonexistent. Photos of alleged polyeuctes chrysalides I found on Google were inconsistent--come to think, some photos labelled as adult polyeuctes online are obviously of other species, too.
The Reiman Gardens web site reports that other polyeuctes usually place one egg on a vine, on the underside of a new leaf, but they're not as careful to do this as some of the Atrophaneuras need to be. Apparently polyeuctes caterpillars are clever enough, as some caterpillars are not, to notice when a skin of their own species is not a discarded skin of their own that they need to eat to discourage predators following them, but is being used by a different animal. All caterpillars have very keen senses of a few things and incredibly dull senses of most things, and yes, many swallowtail caterpillars' instinct to eat their own discarded skins overrides any recognition that a sibling would prefer to keep its skin.
This web site guesses that the caterpillar tries to resemble a dropping of a very sick bird rather than a stick or a leaf, because if an Atrophaneura caterpillar didn't fit that general category of caterpillar camouflage it would have attracted some attention. The pupa probably tries to resemble a dead leaf, despite the existence of pretty photos of pupae shaped like Monarch pupae that seem to be about to eclose into yellow butterflies, currently misidentified as polyeuctes. Confirmation of these guesses is not available online, except that, when otherwise reliable authors generalize about the life cycle of the Atrophaneuras as a group, they don't mention polyeuctes as a conspicuous exception. How it might be possible to tell young polyeuctes apart from other young red-bodied swallowtails, online sources do not say. Funet apparently had a large collection of documents from the eighteenth, nineteenth, and twentieth centuries before the latest Windows update made most of their documents unreadable.
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