Monday, March 4, 2024

Butterfly of the Week: Mansfield's Three-Tailed Swallowtail

This week's butterfly is such a rarity that its Latin and English names make sense. It is one of the four recognized species of Bhutanitis, which literally means "from Bhutan" but is properly translated by "three-tailed swallowtail," and it's named after a naturalist called Mansfield. In Latin, Bhutanitis mansfieldi.  


Photo by Catfish1987, who said it was taken high in the mountains in Sichuan.

It lives in China. Not much information about it has been posted online, and much of what's been written about it was written in (no points for guessing) Chinese. A very detailed description of this species has been preserved online at


In summary, mansfieldi does too look different from other species in this genus if you can get close enough to look at the claws on its little feet.. 

The upper side is vividly colored, perhaps especially in males but also in females.


The underside shows the same color pattern, but is pale and reflective, making the butterflies hard to spot from below.




Photos from Lepidoptera.eu.

Wingspans average three or four inches, making these butterflies easily four times the size of more typical butterflies. Museum specimens displayed alongside other butterflies found in cool mountain regions look immense.

B. mansfieldi looks somewhat similar to lidderdalei and ludlowi. Although their food plant is a vine in the genus Aristolochia, they are classified as Parnassinae rather than Troidini because scientists classify butterflies according to the structure of their wings, first. Within the Swallowtail family, the pattern of wing venation in Bhutanitis' big black wings is more similar to the pattern in the little white Archons' and Allancastrias' wings than in the Atrophaneuras' and Papilios' big black wings.

All the Bhutanitis are rare and in the mid-twentieth century, when chemical "pesticides" were used most recklessly and many species went into deep declines, mansfieldi entered the realm of legend. Some entomologists dropped it from their lists, on the reasoning that, if it had ever existed as a distinct species, it no longer did. Like ludlowi, mansfieldi was rediscovered--in 1981. It was rediscoveed by two Japanese naturalists, one of whom died of a fall on the journey, so this species, too, can be said to have "blood on its wings." The other naturalist, a Mr. Umesawa, died more recently at a relatively reasonable age. For several years Umesawa was known as the only living man who had seen a living mansfieldi. He probably never really deserved this title, and gave it up as other naturalists confirmed his discovery of this species. Still, a great deal remains to be learned about these high-altitude butterflies.

It is, of course, protected by law in China. The Chinese government has had to be brutally practical about other things in order to get away with bitterly clinging to socialism, however, and several of the available studies of mansfieldi are analyses of the biochemicals found in their dead bodies. rather than pretty little articles about the rare butterflies as tourist attractions. Well, to be fair, they fly higher than the average tourist cares to hike.

A similar butterfly with slight color variation was named B. pulchristriata (Latin for "pretty striped") and later classified as a subspecies of mansfieldi. The subspecies name often appears as pulchristata.

B. mansfieldi is found in the same mountain ranges as B. thaidina, the Chinese Three-Tailed Swallowtail, but it flies earlier. Specimens were "collected" while snow was on the ground, proving that these cold-blooded animals absorb heat from sunshine very efficiently.

Male and female mansfieldi look about the same in flight. Some differences were consistently observed between male and female specimens pinned in a laboratory. At close range both sexes have quite a lot of hair, even on the face; furriness may help insulate them against cold weather, and may also help hold and concentrate the scents butterflies use to recognize one another. 

After mating the female mansfieldi, unlike other Bhutanitis, displays a sphragis. In mansfieldi the sphragis is a small white spot or stripe, not the elaborate mess formed by the clear-winged swallowtails. A document about this species that is available for sale online examines the reproductive system of this species in an attempt to understand how and why the sphragis may work. The sphragis is formed by the chemical interaction between male and female butterflies when they mate; it makes it easy for males who are looking for virgin brides, which is most male butterflies, to ignore females who have already mated, and makes second matings take longer, but it does not actually prevent the female mating again if she and her second mate are determined. The secretions that dry out and form the sphragis can also soak and dissolve it. On close examination, the other species in this genus tend to form something like a sphragis, but theirs are smaller, less conspicuous, and often seemingly "incomplete." 

The habits and life cycle of mansfieldi remain to be documented.

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