Butterfly of the Week: Crassipes

This week's butterfly is another one that's been called by many names. When the original swallowtail genus, Papilio, was split up, the black-winged, red-bodied or red-spotted swallowtails were reclassified as Atrophaneura. Then some of the Atrophaneura with red spots on their wings were reclassified as Byasa. English names have also varied; the butterfly is most often called Black Windmill. But its Latin species name has been constant--crassipes, "thick foot," the Bigfoot butterfly.

You can see why. It's one of the larger swallowtails, with a wingspan up to 6 inches, and the hind wings, which are black above and red or pink-spotted below, trail out behind the body as it flies or walks. Museum specimens usually have the wings spread out to form a very broad x shape. 

Images from Ifoundbutterflies.org; click to enlarge and read the phtographers name.

Like most very large butterflies, Byasa crassipes is usually found in warm, damp places. It lives in tropical forests that are considered "dry," with four to five feet of annual rainfall, black soil, and deciduous trees. It's listed as a native of India, China, Burma, Laos, Vietnam, and neighboring countries. Though rare in most of its range, with some endangered populations, the species as a whole does not seem to be endangered. Nevertheless it's on watchlists in Burma, China, India, and Vietnam. In India it is protected by law from endangerment by logging.

Little is known about this butterfly's life cycle. It's been found only once in Thailand, where the presence of even bigger butterflies causes it to be called the Small Black Windmill. There's some question whether it really is or ever was native to China.

Very large butterflies and moths tend to be sparsely distributed across a wide range. In India, in 2018, the presence of one Black Windmill near the site of a controversial new dam made headline news; apparently people have continued waiting to see others, to find out whether the area is part of the butterflies' habitat. 

The precise location of the butterfly that blocked dam building activity was not reported. Too many of the photos of Byasa crassipes online are of dead specimens in museums and there was still concern that, short as their lives are, the big-footed butterflies' lives would be shortened even further by ill-advised "collectors." My generation did grow up, after all, reading first books about butterflies that told primary school butterfly enthusiasts how to catch butterflies in nets, kill them quickly, and pin the bodies into display boxes. Some of us seem not to have received more recent warnings that killing living butterflies is inhumane because it may lead to local or subspecies extinction. Big butterflies don't face obstacles to reproduction as overwhelming as big moths do--the butterflies do eat--but their sparse distribution means that they don't find mates and host plants for eggs easily. 

One should never kill a butterfly before its time. The purpose of preserving dead bodies was to be able to keep and share the memory of what a butterfly looked like. Nowadays that can be done much more pleasantly and efficiently with cameras.