This week's butterfly seems to be in no danger of extinction, or even of being ignored. Nevertheless, some of its local populations are endangered, and this causes concern in the countries where this species lives. Byasa alcinous, to use its most current name, is so popular that we might study it for what it has to teach about popularity.
Photo by Maria Jose on Pinterest
The early researchers who called it Papilio alcinous were showing a preference for this species. Unlike the characters for whom some of the dark-winged, red-bodied Swallowtails were named, Alcinous was remembered as being nice. (In the Odyssey he might be a little too kind. After greeting Odysseus politely, a matter of routine as he's a decent man, he starts to show selfish interests. Odysseus has a wife, Penelope, who we know loves him because she prefers to wait for him to return rather than marry one of the other men who are constantly offering her rich gifts. Ignoring Odysseus's marriage, Alcinous wants Odysseus as a son-in-law.) Though aging, in a period when monarchs were chosen for their prowess in single combat and deposed or killed as soon as younger men beat them in fights, Alcinous plans his retirement in a gracious way suggesting that he has been a good king of his island.
As more distinct species of Swallowtail were recognized, naturalists split that genus, first listing alcinous among the Atrophaneura since it has those dark pin-striped forewings, then splitting it off into Byasa since it has that distinctive wing shape. The genus name Parides alcinous is also sometimes found. Those who prefer English names usually call it the Chinese Windmill since it's one of the Swallowtails whose wings can be spread out to form an almost symmetrical x shape, although the forewings are much broader than the hindwings.
Since they are large and abundant, the species has been well studied. Chinese researchers have mapped the entire genome; sub-species have been identified, and one sub-species is sometimes regarded as a distinct species with identical wings but a different body shape, Byasa confusus.
As their name suggests, these butterflies are found in China, on most of the islands of Japan, and in India, Nepal, Laos, Korea, and other parts of Asia. They are rarely found as far north as Russia. There can be two or more generations in a year, depending on climate. One factor in their popularity is that they coexist well with humans. They are woodland dwellers, but people often see them and learn to recognize them.
In a bid for sponsorship, Bart Coppens used his right hand to snap shots of Byasa alcinous on his left hand. Though intelligent as butterflies go, swallowtail butterflies aren't clever enough to learn to pose for a gallery of photos with a human. I suspect this gallery was created by sticking a dead butterfly's feet onto drops of adhesive, which would explain the odd little patches of lint on Coppens' hand. Anyway it does show the animal's size--a little bigger than the European and most North American Swallowtails, not a great deal bigger. Wingspans range from 75 to 100 mm (3 to 4 inches).The gallery at https://www.flickr.com/photos/75668720@N05/26679580960/in/photostream/also shows how the butterfly's wings reflect light. At some angles they look black, at some angles light grey with the black pinstripes.
They also have a cheerful color. Their big wings can be translucent. Photographed against the sky, they may look bluish. In some lights, some individuals look white. In sunlight, they can look bright yellow. Looking cheerful contributes to popularity.
Photo donated to Wikipedia By 岡部碩道 - Own work, Public Domain, https://commons.wikimedia.org/w/index.php?curid=11210908
They also have generally clean habits. Some people turn against butterflies when they realize how many butterfly species are composters. Though they look prettier and don't lay eggs in nasty stuff, many butterflies' attitude toward dung and carrion is typical of, well, flies. Some butterflies annoy wounded people and may spread infections from one wound to another as they slurp up blood, lymph, and serum from wounds. The red-bodied Swallowtails, however, generally get most if not all of their nutrients from flower nectar, and like to pollinate flowers humans like to keep in gardens. Clean habits also contribute to popularity.
Photo donated to Wikimedia by Hectonichus.
Female alcinous are slightly larger and brighter in color than males. In bright sunlight, some females are likely to be described as yellow or gold rather than black, though in dim light they're described as "dark yellow-gray" with blackish pinstripes. This yellow undertone can also make the female's red spots look orange. Bodies generally show black or grey on the back and some red on the sides; from a side view some butterflies' bodies look bright red, some are blackish with reddish markings, and some are dark with red patches only on either side of the posterior segment.
Two males and a female from Japan's Takao Museum.
Females may also be "brighter" in learning ability; about ten years ago Japanese scientists tested these butterflies and found that both males and females learn to recognize the flowers they most enjoy pollinating, and females learned faster. Young butterflies will sip the nectar of several flowers once. Older butterflies will ignore the flowers that were less satisfactory to them and concentrate on the kinds they liked best. For forty dollars, the scientists will reveal which flowers the butterflies like and guess why.
A female alcinous normally mates only once. Though these butterflies fly for only about two weeks, so the female is not naturally motivated to find multiple mates as a female Monarch might be, researchers trying to breed them in cages tried forcing their specimens to mate repeatedly and found that, rather than increasing, multiple matings decreased the numbers of viable eggs each female produced. (Males? Like males of some other species, they'll sleep around if they can. No data is available on whether multiple matings affect the reproductive success of males.)
Male alcinous have an odor that even humans notice, and the Japanese name for these butterflies, jyako ageha, translates literally as "musk butterflies."
Like the other "Windmills," they use their two pairs of wings separately to fly. Most butterflies seem to get best results by flapping the two wings on each side as one, but the Windmills seem to use forewings to press forward and hindwings to steer. When perched, the forewings may be raised over the body while the hindwings trail down behind.
After mating the female butterfly spends most of the rest of her life flitting around different Aristolochia plants, crawling about on each plant, deciding where to place her eggs. While she appears to be thinking seriously about the prospects each leaf offers for one of her babies (and there's no way to prove that she's not), she's actually reacting to chemical stimuli. She "tastes" the chemicals in different leaves through her feet, and lays eggs where she tastes a sufficient amount of the right chemicals. Researchers have trapped female butterflies in cages containing chemical-soaked paper, and the butterflies laid eggs on the paper.
Caterpillars live mostly on three species of Aristolochia, and their looks and life cycle are affected by the quality of their food. Japanese farmers often mow or cut back Aristolochia kaempferi to stop the plant invading crop fields, roads, and paths. While this does not kill the plants or necessarily harm the caterpillars, "disturbed" Aristolochia kaempferi produces tougher leaves and stems, which seem to take longer for the caterpillars to digest and cause them to mature more slowly than they would if they were eating tenderer leaves. Spending more time as a caterpillar increases the chance of an individual's being killed before it can become a butterfly. Additionally, in an indoor laboratory, caterpillars fed on tougher leaves formed brown chrysalids preparing for a long hard winter, which would have reduced their chance of survival by putting their biological clock in opposition with the rest of their environment. Even without the additional hazards of pesticide vapor drift, even natural land management may be reducing populations and endangering sub-species of alcinous on northern Honshu island. (The species does not seem to exist on Hokkaido at all.) Overall, the caterpillar's "plasticity" of reactions to food quality, probably to humidity and light, and to temperature as it prepared to pupate probably contribute to the species' ability to survive, forming sub-species, at different latitudes and altitudes.
Photo donated to Wikipedia By Cory, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=3004292.The caterpillar is a big bluffer. It's actually easy for a large bird to swallow, though difficult to digest due to the amount of aristolochic acid it contains. But it wants to look bristly, even to confuse predators about which side has the little claws it might be able to use to resist being swallowed!
The color of pupae reflects the adolescent butterfly's condition and the length of time it may take for the adult butterfly to emerge. Butterflies that pupate in summer don't go into a dormant phase; their pupae look yellow. Butterflies that do go through a dormant phase look brown, and remain dormant for several months to get through the long winter.
Photo donated to Wikipedia By MUSASHI-Sakai - オリジナル, Public Domain, https://commons.wikimedia.org/w/index.php?curid=7717999. This chrysalis would normally be visible in summer, and would look from a distance like a mold-blighted leaf.
Chrysalids found in Saitama, Japan. These chrysalids would normally be attached to large dead leaves and would look from a distance like smaller dead leaves.
Individual alcinous that pupate in summer often pupate right on their food plants; those who pupate in winter often hide among dead leaves.
Shun Takagi took time-lapse videos of alcinous caterpillars pupating and emerging as butterflies. Months of real time are here summarized in a three-minute video:
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