Читать книгу Magdalena Mountain - Robert Michael Pyle - Страница 21

Magdalena Mountain melts. At least its white carapace melts and slides away down avalanche chutes, sublimates into the alpine sky, or is sucked into stony rivulets by the thirsty warmth of spring. Blackened mosses along those rills regain their green as the running snowmelt fills their sponges and swells their thalli. The first of the flowers burst out—marsh marigolds in the wet edges, glacier lilies beneath the shrinking snowloads, pale mauve pasqueflowers down where the limber pines wrestle with the rocks in perpetual border dispute over timberline.

These early floral offerings are not without their croppers, for the diminishing cold grows too weak to hold pikas in their places. The gray harelets, a little less round than last autumn, pop out and eagerly see to the pruning of the early-spring vegetation. This is turning out to be a wet and lush year, with plenty of runoff and succulent regrowth, so no desperate pika or poor skinny coyote grazes the strawlike clump of grass at the edge of the rockslide where Erebia is coming back to life. About the size of an apostrophe, he shares that character’s round black head, a feature that sets him apart from the young of the other three species of Colorado alpines. The rest of his body is colored pale flesh with purplish stripes. A greenish cast will overtake it as the grass’s chlorophyll passes down the translucent tube of his hungry gut.

Activity accelerates on the scree, where so recently the only movement was white crystals falling or blocks of them breaking away. Now screaming flocks of silver-gray, black, and white birds—Clark’s nutcrackers—swoop from one patch of pines to the next. Related ravens too pass upslope and over the rocks, kronking, their great black shapes foreshadowing the smaller ones that will mime their flight after another moon’s circle. When the ravens cross overhead, pikas squeak eek! and dive for the safety of their crevices. When any big shadow could as well be a raptor as a corvid, why take chances?

Marmots at last shake off their somnolence and begin to bask on reflective slabs of granite. Soon their whistles will be heard, an academy of traffic cops shrilling contradictory commands from every major intersection on the mountain.

Erebia remains insensitive to all these goings-on. Only the rising, falling temperature rules his day, along with the intensity of the sunshine, such that he can seek the shelter of the grassroots when nightfall threatens late frosts. The duration, too, of the sun, for the gathering daylength quickens his hormones even as the rising sun thaws his muscles. Subject to desiccation at the drop of a dry grass blade, Erebia constantly seeks the dampest patch of turf, often resting on a spongy clump of moss or moss campion to maintain his water balance.

Now Erebia’s sliver of a larva faces many dangers. Ground beetles, spiders, woodlice, ants, and many other creeping predators prowl the sparse vegetation, ready to catch and consume his tiny packet of protein. Parasitic wasps and flies probe his haunts. But the greatest threat comes from the presence or absence of moisture: too much means mold; too little, death by crisping. Any fool who has tried to rear mountain ringlets and graylings knows this. But Erebia finds his needs, is not himself found, and so he grazes and grows.

Then, not many days after spring breaks out on Magdalena Mountain’s southeast flank, at eleven thousand feet, Erebia reaches the point when his skin can stretch no more. Taut, sleek, and bulging, it splits, and along the new suture a softer, deeper green skin shows through. Like any dry seed erupting, cotyledon unfurling, atom splitting, the new form lunges into the come-what-may with vigor. This is Erebia’s first molt of five—a shedding, a rebirthing that some of his siblings already experienced last fall, before their winter’s diapause. Now, out comes a more supple and pliant caterpillar, bigger, the size of a shaved pencil point, his head still black but his tube suit gray-green and darker striped.

Erebia eats more, no longer restricted to the baby food of the softest blades, and so grows faster. He has it in him to go either way: if heavy weather or an early snowfall should cut short the season, he can reenter that state of winter grace and pass a second season of chill. After all, many alpines are routinely biennial, taking two full years to mature. But, for the robust black Erebia magdalena, just one year usually suffices. So this particular wee one feeds on, and feeds, and feeds some more.

As he grows, Erebia’s range of potential predators only broadens. Rockslide rodents, passing bands of rosy finches, nesting pipits patrolling their territories, any of these and many more would readily snap up this black-tipped wormlet for an iota of their day’s nutrition. Many of his brothers and sisters become such bites. But this one has the luck with him, and four more molts will follow in their time, each one delivering a larger, more succulent animal.

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.