The genus Battus is American but has several points of resemblance to the Atrophaneuras. Though all Battus are in the swallowtail family, some of them have "swallowtails" on their hind wings and some don't. In the species Battus belus, most subspecies are tailless but some have tails.
Battus belus does not have a generally recognized English name. Of the suggestions Google offers, I like "Midnight Swallowtail" best, but you have to be familiar with the color Binney & Smith's Crayola crayons label "mdinight blue." It's a rich, complex, almost metallic dark blue with both green and purple undertones, like the wings of iridescent black-blue-green birds and butterflies. It's also called the Belus Swallowtail, which looks like a misprint in English, and the Golden Swallowtail, which sounds like a name for one of the yellow species. But does "Midnight" do justice to those individuals of this species whose color is distinctly greenish black? Is it an accurate name for a day-flying species?
"Triple Cream" is sometimes found, but seems to describe only the minority who have large cream-colored (or white or yellow) patches on the fore wings, white or yellow upper borders on the hind wings, and white abdomens; people who write about "Triple Creams" often can't even find a specimen of that pattern to illustrate their posts, so it's not as if the "Triple Cream" pattern were even the dominant pattern in some places. "Midnight" at least describes a common and noticeable pattern, if not the most common or noticeable.
Both Battus amd Belus were minor characters in the story of Hercules. I don't like Belus as a butterfly name, because it's a different word from bellus, "battle, war." Though later Greek and Roman authors treated it as a man's name, it is that pan-European word for "Lord and Master" by which the gods of various cults became known. Butterflies don't own anything, any more than they know anything about war.
What about bella, the word for 'beautiful" in this butterfly's habitat? Would people agree that they are beautiful butterflies?
Since English names for butterflies tend to stick only when they describe the butterflies' looks, and this species doesn't have a single memorable look, it may have to get by with multiple English names.
Males look more alike. Subspecies are defined by the different color patterns typical of the females, who can be bluish, greenish, or brownish black, with or without white or cream-colored, yellow, or red and blue spots. Abdominal segments are often chalky white; thoracic segments, and the head, are usually black, often with polka dots of white and/or color. Often, though not always, there is a white stripe along the upper edge of the hind wings where the wings overlap. Wings can be somewhat translucent.
Photo from the Reiman Gardens.
"Triple Cream" subspecies varus can have a large cream-colored spot on each forewing, conspicuous both above and below, and some white or cream-color on the abdomen. The photos I saw did not show the cream-colored border at the top of the hind wings, which is visible only on the upper surface and usually covered by the fore wings of living butterflies; it is visible on some museum specimens.
"Golden" subspecies cochabamba has bright yellow patches where other subspecies have white patches or none.
This tropical species is usually found near the equator in Brazil, Costa Rica, Ecuador, and Guyana. Though some other butterflies in the tropics are bigger, it still tends to be noticed as large, with a wingspan of 3-/1/2 to 4 inches. Females tend to be just noticeably bigger than males.
Before research persuaded scientists that these different-looking butterflies all belong to one variable species, many species names were proposed for the different forms. Some of these names are still used for subspecies. Various subspecies, genders, and color morphs of Battus belus have been written up as Papilio numitor, Papilio amulius, Papilio caburi, Papilio varus, Papilio heteropterus, Papilio belus chalceus, Papilio belemus, Papilio cochabamba, and Papilio belus gastoni. Heteropterus refers to the fact that a few specimens have been found with different color patterns on left and right. Here's a vintage discussion of these different looks that have turned out not to be different species, much too long to be copied:
The velvety green upper wings of some females fascinated Victorian artists.
Walter Rothschild and others tried to work out a pattern in the variations and intergrades that eventually suggested to naturalists that these butterflies really were a single species. I've not tried to figure it out because, reading what's written about this species more recently, I'm not convinced that anyone else understands why they can look so different either. They recognize one another by scent rather than color, and they seem to think they're all the same kind of animal.
Males are most often found at puddles, where they are easy to photograph. Like many swallowtail butterflies, males take some time to become ready to mate. When they do mate, their spermatophores contain minerals the females need. Females can drink brackish or polluted water for themselves, but their preference is to drink nectar and absorb their mineral supplements after mating. So a likely place to find and photograph these species is at a puddle, where males gather to drink water, hang out, and wait to grow up, and females cruise around the edges of these groups of males, checking to see if any of them is ready to mate. Thus, females are primarily pollinators (who occasionally do some composting if driven to it) and males are primarily composters, but some species have cleaner composting habits than others. While Battus belus is much better documented in images than written words, the material I found did not mention this species' showing any interest in carrion.
Though Rothschild speculated that different altitudes might select for the different color patterns, all subspecies of Battus belus are typically found at low altitudes, usually within about 1000m above sea level. Individuals often stray as far north as Mexico and have been found all the way up to British Columbia, but the northern border of the species' habitat is probably in Nicaragua.
Caterpillars eat the leaves of vines in the genus Aristolochia. Unlike the typical Atrophaneura caterpillar, their skins may display warning colors separated into interesting patterns.
Both photos anonymously donated to My Species.
Unlike many swallowtail caterpillars, Battus are often gregarious. Mother butterflies lay several eggs on one leaf and baby caterpillars travel along the host vine in a group, possibly being less recognizable as caterpillars and/or more intimidating to predators that way. People who rear these butterflies persuade the caterpillars to crawl over their hands side by side. Three or four of these large caterpillars cover a human hand at a good healthy distance from one another. The vines grow fast enough to survive and host the caterpillars. As they mature the caterpillars separate into smaller groups as necessary to fit themselves around the stem or along the leaf they are eating, but are still often photographed just a few inches apart. A cluster of eighty Battus belus eggs has been reported. How many of those eggs hatched, how long the caterpillars stayed together as a family, and how widely separated they were when they pupated, was not reported, nor does there seem to have been any effort to determine why the mother was so sedentary. A half-dozen or a dozen eggs, yielding almost as many baby caterpillars or three to four big ones, seems to be a common observation.
Photo from the Reiman Gardens, documenting the pupa's dead leaf pattern.
William James Cooper has a time-lapse video showing a butterfly's eclosion.
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