Natural Acts: A Sidelong View of Science and Nature - David Quammen (1996)

ALL GOD’S VERMIN

Avatars of the Soul in Malaya

CONSIDER NOW THE LEPIDOPTERA, in all their vacant splendor.

They are the bimbos of the natural world: more beautiful and less interesting, arguably, than any other order of animals. An evolutionary experiment in sheer decorative excess, with a high ratio of surface to innards. They move through the air like pulses of idle thought. They have a weakness for flowers. They are prodigiously diverse without being adventurous: roughly 150,000 known species, all of which behave pretty much alike; 150,000 distinct patterns, but in each case a six-legged worm strung between kites. They are silent. Detached and diaphanous. Generally they possess neither teeth nor jaws. They feed pacifically on plant liquids or (some species) just go hungry through their entire adulthood. Fly on wings that are fleshless and papery, flashing bright iridescent colors produced by the devious exploitation of tiny prisms and mirrors. Certainly these are real physical creatures, yes; then again, they just don’t seem to be quite all there. Aristotle was onto something, I think, when in the fourth century B.C. he used the Greek word psyche to mean both “soul” and “butterfly.”

They might be insects. Or they might be platonic ideas.

In classical Greece and then later in Rome, this link with the spiritual realm was applied to both major subgroups of Lepidoptera, the moths as well as the butterflies. Both moths and butterflies were delicate enough to suggest a pure being, freed of its carnal envelope. Both were known to perform a magical metamorphosis—from fat, ugly caterpillar to gorgeous, airborne adult, with a dormant pupal stage in between—that put humans in mind of resurrection from the grave. Moths may have been even more suited than butterflies to bearing this burden of symbolism, in that moths, like ghosts, fly at night. Tomb-sculpture designs from imperial Rome have survived (thanks to later Italian scholars, who copied them before the original stones were lost) on which appear butterflies and moths carved to represent the departing souls of the dead. And the motif has endured. One marker from a nineteenth-century grave in Massachusetts shows a common monarch, Danaus plexippus, freshly emerged from its chrysalis and winging away—the soul as butterfly.

Clearly mankind has taken some small comfort over the past couple millennia from gazing upon Lepidoptera and positing this odd connection between their substance and our essence. Why the Lepidoptera? Maybe it’s because they are detached and diaphanous, because their beauty is of an otherworldly sort. No sting, no bite, no bothersome buzz. Strict vegetarians. They represent an ideal of sweetness and gentle grace that seems almost innocent of the whole merciless evolutionary free-for-all. No wonder they are, zoologically, so godawful boring to contemplate.

But wait. That’s only the traditional, happy-time view of the Lepidoptera. It applies to no more than about 149,999 species. And it takes no account whatever of a small Malayan jungle moth called Calpe eustrigata.

Here finally is a moth with character, a moth with edge, a moth unafraid to besmirch itself in the Darwinian struggle. A moth unique, among all known moths, for its dietary behavior. Calpe eustrigatasucks blood from humans.

There is no common name for Calpe eustrigata, but it belongs to a large family of drab little moths called the noctuids, notable in this country mainly for the damage that larvae of some species do to vegetables and grain. These are your basic cutworms and ear-worms and celery-loopers. Such dreary noctuids can be plentiful, species by species, but C. eustrigata is quite rare. It was discovered some decades ago by an admirable fanatic named Hans Bänziger, a Swiss entomologist who was spending two years in the jungles of Thailand for research on a different group of noctuids.

In Thailand the work progressed satisfactorily; the moths behaved more or less as expected, and there was no sign of any such creature as C. eustrigata. Toward the end of two years, Bänziger got down into Malaya (as peninsular Malaysia was then called), where he wanted to investigate several species that were opportunistic blood-drinkers of a purely nonaggressive sort. These Malayan moths were known to lick at the open wounds of large mammals and to follow after mosquitoes (which are greedy and slovenly as they extract blood), lapping up what was spilled. Again the moths behaved as expected. At least they did until, late one night, Bänziger captured a particular specimen. He found it alighted on a water buffalo.

Bänziger’s own account, from a back issue of the journal Fauna, sets the scene: “I had become suspicious of this insect species because of a photograph taken a few days before while it was feeding on a Malay tapir. The photograph showed something very strange about the moth’s proboscis. Now with a live specimen I intended to study its feeding behavior on myself. That night was to become especially exciting! Having incised my finger with a scalpel to draw fresh blood, I offered my finger to the caged moth. The moth climbed onto my finger and did in fact plunge its proboscis into the blood, but it appeared to imbibe none. Instead it stuck its straight, lancelike proboscis into the wound and, without any regard for the donor, penetrated the flesh. The pain I felt caused me to utter a cry of—joy!” Lucky the man who so loves his work. “I had discovered a moth which pierces to obtain blood.” If you were a lepidopterist, you’d see that it was a pretty big moment in history.

During a month in Malaya, Bänziger found only twenty-four more specimens of C. eustrigata, but he kept them busy poking and sucking at his hand. As an experimentalist, he lacked nothing by way of commitment. “Blood-sucking occupied from 10 to 60 minutes and blood continued to flow out of the wound for a few minutes after cessation. Hours and sometimes even days later, the wound was still itching.” The remarkable aspects of all this involved not just the matter of behavior (including Bänziger’s behavior) but the matter of anatomy. Lepidopteran mouth structures are totally different from those of, say, a mosquito. The standard equipment for butterflies and moths is a long flexible tube that remains coiled up under the head until, when needed, it can be sprung out straight by hydraulic pressure, like one of those paper noisemakers in the mouth of a drunk on New Year’s Eve. In extended position it allows the insect to suck nectar from the reservoir of a deep flower. But this thing is a drinking straw, not a drill. Until Bänziger, no lepidopterist had ever seen a moth whose proboscis could be stabbed through human flesh.

There was also the mystery of its evolution. Where had C. eustrigata come from? How had the bloodsucking adaptation, along with the equipment to practice it, arisen? What were the intermediate stages between Bänziger’s new species and those other Lepidoptera—all 149,999 of them—who noodle from blossom to blossom drinking nectar through their elongated schnosters? What manner of temptation could have lured certain moth species astray, turning their tastes from flowers to blood?

The answer, it seems, was fruit. Faced with mortal competition over limited supplies of nectar, a number of noctuid species have adapted themselves to feeding on the juices of overripe fruit. Some have developed stronger and sharper mouth tubes that allow them to pierce the skin of soft fruits, such as peaches and raspberries, and suck out their fill of juice. One species is even armed with a proboscis that will penetrate the skin of an orange. Among these fruit-piercing moths are several close cousins of C. eustrigata. Bänziger suggests that in a habitat where fruit was available only seasonally but juicy mammals were present year-round, desperate necessity might have led to the next logical step: vampirism, as practiced by moths.

But the vampire moth was just a distraction from what had taken Hans Bänziger out to Southeast Asia. He was there to study a group of species he called, rather blandly, the “eye-frequenting” Lepidoptera—moths that literally live on a diet of tears.

These wondrous creatures may have evolved from the opportunistic blood-drinkers that clean up after messy mosquitoes. Bänziger says: “Probably by crawling about on their mammalian hosts some moths found the eyes, where there are always discharges. And thus there evolved the habit of dining exclusively upon eye discharges, which contain various proteins such as globulin, albumen, and others in the leucocytes and epithelial cells in tears.” Such moths, in the wild, would drink from the eyes of elephants. They would drink from the eyes of horses, buffalo, antelope, or pigs. And as Bänziger demonstrated with his characteristic élan, given a proper opportunity, they would drink from the eyes of man. “The lachrymal secretion was very much stimulated by the activity of the moth. After 30 min. my eye was so irritated that I was forced to interrupt the experiment.” Only thirty minutes of moth-in-eye jabbing, imagine, and he called a halt. But not before the insect had drunk freely from Bänziger’s own tears of—joy! There is even a photograph showing a small noctuid of the species Lobocraspis griseifusa perched head-down across Bänziger’s brow, its tube extended to drink fluid off the surface of his cornea. “Note the deep penetration,” reads his unblinking caption, “of the proboscis between eye and eye lid.”

Note the deep penetration of Lepidoptera between fact and imagination. I suspect that the Greeks and the Romans would have known what to make of Lobocraspis griseifusa, a species in the spiritual tradition. Imagine how Ovid would have loved those insects. The souls of the dead return, on powdered wings and in silence, to comfort mankind; to console us earthbound survivors; to drink away our very tears

It’s a nice thought—too nice to be true. But the intricate realities of evolutionary entomology don’t lend themselves so well (no better than other branches of nature) to our neat romances and our pathetic fallacies, and these two species stand as vouchers to that truth. If we idealize the tear-drinkers, then what about the suckers of blood? A moth, hungry animal, is only what it is.