More than halfway through the long list of dark-winged, red-bodied swallowtail butterflies found in subtropical and tropical Asia, we come to the "Windmill"-shaped species currently known as Byasa nevilli, or Nevill's Windmill. It was documented late, in 1882. A lot of material about it has been placed on the Internet since Mr. J. Wood-Mason of the Indian Museum at Calcutta described it:
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Papilio Nevilli, n. sp.
Papilio, n. sp,?, G. Nevill,,.List Diurn. Lep. Ind. Mus. Cale. 1871, p. 1. no, 7. Nearly allied to P. ravana, Moore, from Kulu, in the Northwest Himalayas, but smaller, with the well-developed tails not constricted at the base.
[Male]. Posterior wings above with two large pink-white spots, one between the discoidal vein and the second branch of the subcostal, occupying all but the two ends of the space; the other in the space next in front, smaller and not extending so far towards the base of the space, and with three bright crimson submarginal lunules, two subequal in the interspaces between the branches of the median vein, and the third between the third median veinlet and the discoidal vein, equal to, or slightly greater than, the other two taken together ; below with a small pink-white spot between the first branch of the subcostal and the costal veins, forming with the two visible on both sides of the organs a series of three, all equally distinct from the outer margin, the submarginal lunules larger and subequal and much lighter coloured, and with a fourth rather irregularly-shaped crimson spot, subequal to the lunules and divided into two unequal parts by the submedian vein, at the end of the basal half of which it is placed, with the tails well developed, but not constricted at base.
Hab.The vicinity of Silchar, Cachar. The three specimens before me were obtained many years ago by one of the native collectors of the museum, under the late Mr. N, T. Davey, of the Topographical Survey of India.
_ This species will be figured in my paper on the large collection of butterflies formed by me during the past hot season in Cachar.
Obs. P. ravana and P. minereus are both perfectly distinct from P. philoxenus, P. polyeuctes being perhaps only a variety of it.
"
Photos from the Reiman Gardens.
B. nevilli has been given even more names than the other butterflies in this group. First called Papilio nevilli, it's also been documented as P. chentseng or chentsong, Tros nevilli, Atrophaneura nevilli, and lately Byasa nevilli. A few sources use nivelli, probably a mere misspelling. Both "Byas" and "Nevill" are family names but my sources did not specify which members of those families the butterflies were named in honor of. ("Byas," for our international readers, is pronounced like the word "bias," and Byasa is generally given enough of a secondary stress on the second syllable that the short A as in hat can be clearly heard.)
One alternative English nickname was "Two-Spotted Windmill." The photos show why the butterfly was given that name, and why the name hasn't stuck.
Most Indian butterfly species, including B. nevilli, were documented and "collected" by the British Raj. The Rothschilds, among others, bragged about a "family collection" of Papilio nevilli. However, that shortsighted fascination with collecting dead bodies of different kinds of butterfly didn't help modern scientists with what we want to know about them, laments Subrata Gayen. Nobody knows whether butterflies are threatened by climate change, habitat loss, or use of pesticides and/or GMO in India, because nobody knows what their normal population size and density used to be. Nevill's Windmill is not known ro be endangered but it is of concern in India. It is now "very rare." Is it, like so many of the big butterflies and moth, a species that needs to be rare? How rare? Is its population decreasing or increasing, and how bad as that? Nobody really knows.
For even more complicated historical reasons, some of which Torben Larsen discussed in Butterflies of Bangladesh ([published as a book, and online as a PDF at https://www.flutters.org/home/articles/2004%20Bangladesh%20book%20716%20KB.pdf ), the butterfly populations of the smaller countries in between India and China are "very poorly known." What little research did go on has left us with a few collections of crumbling carcasses marked only with old state or country names, or at best species names. Nobody was bothering to study where and how the butterflies lived or how many of them there were before "modernization." Larsen reported that by 2004 it had become difficult to get permits to collect butterfly carcasses for scientific research, though butterflies will always continue to leave their bodies to science after flying for a few weeks, and yet vendors were continuing to sell carcasses in glass cases, with fresh-looking "perfect" wings, to tourists.
Byasa nevilli is said to be common in western China; China, however, has not made a priority of either documenting or conserving its unique wildlife. Its wingspan is 10 to 12 cm, 4 to 5 inches. Males resemble Atrophaneura dasarada ravana and/or Atrophaneura ravana (some list ravana as a separate species, some as a subspecies of dasarada), but are smaller and have smaller spots. Ravana shows more conspicuous sexual dimorphism than nevilli; female nevilli look more like male nevilli than like female ravana.
The caterpillars eat Aristolochia kummingensis, a tropical vine that contains aristolochic acid and other chemicals that are toxic to warm-blooded animals. These chemicals remain in the butterflies throughout their lives. Eggs show tiny patterns formed by drops of aristolochic acid; other phytotoxins from the host plant give the animals their black and red colors, which blend together in the caterpillar's skin and form distinct patterns on the adult butterfly. Black and red are "warning" colors for insects--typical of species that are at least foul-tasting, sometimes nauseous or toxic, to birds. After eating an orange, black, red, yellow, or blue insect, an animal that has the ability to vomit will usually do so.
The pupae have that flattened dead-leaf look typical of the red-bodied swallowtails.
Another photo from the Reiman butterfly gardens. (Part of the fun of writing these pieces is seeing my Google searches actually fuel site expansion. This niche is still small enough that individual searches can affect results. Reiman was showing only the two photos when I opened the page, then added this one a few hours later.)
Adult butterflies fly for about ten days. It's easy to collect dead bodies if you're in the right place on the right day, but only chemists have any use for dead butterflies these days. Modern butterfly fanciers collect photos of living butterflies, The English-speaking world is still poorly supplied with good clear pictures of Byasa nevilli.
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