Nearing the summer solstice, Erebia slips into his final instar. Now he would be readily recognized for what he is—no tiny worm of indeterminate nature, but an actual caterpillar, precedent to butterfly or moth. A handsome animal he is as a mature larva, spring-green, lined and diagonally slashed with white. Now nearly an inch and a half long, he bends the grass blades over when he climbs them, like a child on a small aspen. His shape is that of a streamlined dirigible, tapering toward twin tails at the stern, thickening to that shiny, still-black head capsule: a black helmet to keep his brain ganglion warm, allowing longer feeding, greater alertness, faster development. That jet headpiece shines in the undeflected high-country sun.
Erebia’s striped pattern and grassy coloration render him cryptic among the tussocks, confounding predators that by now would find him a more than worthwhile morsel. So refined is this crypsis that the majority of larvae reaching this stage (a small portion of those hatched last summer) will now survive to pupate. Because by now, color-sighted birds are the chief threat rather than creeping, tapping invertebrates. The new, mottled chicks of ptarmigan present a particular peril to Erebia and his like. Their parents eked their way through winter, white on white, stuffing themselves on willow buds before bundling under the snow for the night. But the new hatchlings need protein for rapid growth during the brief season when insects are available, so they work the greening sward like hens and chicks scratching their way across a barnyard. By chance and grace, no pecking ptarmigan or jabbing jay comes across Erebia.
So it is that in the last week of June, a final molt takes place. This time no larger, greener caterpillar comes out. First, Erebia goes walkabout for many yards—a risky, exposed procession, but one almost every caterpillar undertakes—negotiating sedge and stone, exposed and parching bare spots, and soaking mountain moss. Under and over the lichened rocks he wanders, across the pygmy savanna of alpine sedges and forget-me-nots. Finally he winds his way into a random wickerwork of last year’s grasses, where he turns around, catlike, several times, and settles into the scrape. Then his skin splits one last time, he wriggles out of his old bodysuit and emerges as a grublike thing, dark viscous green, like a blob of crude oil in color and shine.
Even before the last used skin fell away, the body it held began to dissolve within. Now the prepupa quickly hardens on the outside into a black, sarcophagus-like case—but hardly that, since the insides are yet quick. These contents soften and fall apart, and their tissues break down almost entirely. A deer mouse biting into the fresh pupa would find no caterpillar, nor butterfly, but a portion of puslike soup devoid of apparent form. Nor does the pupal shell, embossed as it is with butterfly features, damasked with the shapes of wings, legs, tongue, antennae, and eyes, serve as a cast to mold the muddled substance within, to give it the form into which tissues may take shape, as the ancients concluded. No waxen die from some creator’s hand, the chrysalis is a pod of change in which Pan works and plays. His tools are a set of imaginal disks, bundles of cells that direct the reassembly of materials into the adult hard and soft parts that make up a butterfly. Genes direct the scene, and enzymes and hormones carry it to completion.
Thus programmed, the new features come together from the inchoate brew and fill out into the waiting, shaped receptacle of the chrysalis shell. The engraved case then receives the form of the insect rather than tooling it from wet prepupal clay. And in this way, the finer details still obscure and of no moment whatever to Erebia, the black animal that is the Magdalena alpine comes into its improbable adult existence.
A day comes, just two weeks after pupation, when the finished butterfly presses to be released. His casket goes glassy black. Then it bursts open, dehiscing along the dotted lines of its seams, revealing that this was no coffin, but a birthing chamber. It is easy to see why the Arapaho of these summer peaks called the butterfly chrysalis an egg, for surely the pupa is to a butterfly what the egg is to a bird. The shell cracks and falls back, transparent. The blackness, which has deepened from soot to sable, belongs to the creature within rather than to its wrappers. That heavy pellet, the pupa, which seemed so solid as it lay ripening in the summer sun, now lies insubstantial as a November husk long since robbed of its kernel by mouse or maggot. Erebia steps out.
Crawling up a spike of grass, clinging to an overarching stone, Erebia hangs wet and rumpled and limp. But not for long. His swollen abdomen begins pumping. The wings expand slowly, erectile, as the sun-warmed hemolymph courses into their veins. They stiffen like the struts of a kite. Gradually the wings’ oval shape comes clear as the body shrinks to normal proportions. For some hours the wings are as soft as silk and just as delicate. This is a dangerous time, for a fall or a scrape could crush them or prevent their proper expansion. But all goes well. Erebia shimmers with moisture for a few minutes before the droplets evaporate on the dry alpine air, and it continues to glisten with a violet-green sheen imparted by a layer of prismatic scales that will soon fall away.
And beneath the iridescence, black: a blackness so deep that it tells the entire tale of the long night of pupation at a glance, so thick that it hints, if you can see, at the depth of the void that provident evolution has filled with these wings and the body they will carry on high. Black-panther black, black-velvet black, far blacker than starlit-night black, but not as black as a hardrock hole because there is a luminosity to it also.
Such a blackness bears the Magdalena alpine.
This new-to-the-world Erebia magdalena creeps onto a patch of black lichen, warmer than the surrounding sugar-stone granite, and tilts his now-dry wings down against the surface, together. A constant cool breeze tries to chill all tissues, but the sun warms them faster. Soon his flight muscles reach the temperature necessary to work, to lift that black package off the rocks and set it sailing into thin air.
Erebia has passed the survival gauntlet of his profound metamorphosis. He has endured the long sentence of the ground-borne and the parole of the pupa. Now a butterfly, this creature flies free across the mountain’s face for the first time.
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