SPIDERS DO NOT INTIMIDATE Dr. Willis J. Gertsch. When I visited him in his studio-laboratory at the foot of the Chiricahua Mountains in south¬eastern Arizona, he dumped a live tarantula from a glass jar onto the top of his desk. The gray-brown, eight-legged shaggy thing—nearly the size of my fist—was clearly the stuff of which bad dreams are made.
“During a lifetime with spiders,” reflected the scientist, his bare fingers guiding and restraining the restless creature, “I’ve been bitten by tarantulas of a dozen different species. And as you see, I’m still here and in moderately good health.”
The big furry spider prowled inquisitively across the back of his hand. “Regardless of old Hollywood horror films,” Dr. Gertsch continued, “a tarantula bite is hardly worse than a bee or wasp sting, unless you happen to have a particular allergy. As a matter of fact, some ants, bees, and wasps are far more dangerous. But it’s the spiders that always make the headlines.”
Dr. Gertsch had a point. Spiders are among the most feared and maligned of nature’s smaller creatures—and among the most fascinating. An incredible number of species in¬habit the world, but only a dozen or so can be dangerous to man. And, on the other face of the coin, nearly all do their part in keeping in¬calculable hordes of harmful insects in check.
Wind Wafts Spiders Far Out to Sea
One finds spiders almost everywhere—four miles up in the Himalayas, in below-sea-level deserts, in tropical treetops, and burrowed into the earth. Mariners have even sighted them far at sea, drifting on the wind, suspend¬ed from threadlike “parachutes.”
The average life of a spider spans only a year, yet a tarantula may live as long as three decades, and take eight to ten years to mature. Most spiders lead solitary lives, but a few are social, with many individuals sharing a common web. Some species are as small as pin¬heads, others the size of dinner plates. Though many people think of spiders as insects, they are more closely related to ticks, scorpions, and, remotely, to horseshoe crabs.
But chief among the marvels of the spider is its mastery of spinning. I have watched human lacemakers work a spider-web motif into handkerchiefs, napkins, and tablecloths, but the result is clumsy compared to nature’s often exquisite products.
Oddly enough, though, Greek mythology attributes the spider’s skill to human origins. An artful weaver named Arachne impudently challenged the goddess Athena to a contest. Later, shamed and mortified by her own conceit, Arachne hanged herself. The goddess, in a moment of compassion, brought Arachne back to life, transformed her into a spider, and made her noose into a web.
“Live,” Athena commanded, “… and that you may preserve the memory of this lesson, continue to hang, both you and your descend¬ants, to all future times.” And so the name of that superb classical spinstress has been perpetuated by scientists: Arachnologists like Dr. Gertsch study the class Arachnida and the order Araneida—spiders as a group.
Dr. Gertsch amiably coaxed his eight-legged friend back into its jar. Then the scientist, retired after many years as curator of spiders at the American Museum of Natural History in New York City, gave me a quick refresher course on arachnid evolution.
“Spiders’ bodies and habits have become adapted to harvesting insect food supplies in a multitude of habitats. Most hunting spiders prowl on the ground, relying mainly on strength. Keen-sighted wolf spiders and jumpers use sheer speed in overtaking prey. Aerial spiders have devised three-dimensional webs within which they hang upside down (page 219), mazes of lines to entrap crawling insects, and sheets and aerial tangles to intercept jumping insects. And the orb weavers spin round geometrical webs that efficiently en¬tangle flying or jumping insects.”
Dr. Gertsch’s own favorites are the more primitive spiders: American tarantulas, trap¬door spiders, purse-web spiders, and the most primitive of all, the liphistiids, little changed since Carboniferous times, some 340,000,000 years ago.
Walking Factories Produce Varied Silks
In my own exploration of the spider world, I found myself endlessly fascinated by the orb weavers. The raw material of their gossamer creations—a complex protein substance —is manufactured by five or six special glands in the spider’s abdomen, each producing its own variety of silk. Acting separately or in combination, these glands supply dry or sticky threads for lines, cables, and attachment disks for webs; egg sacs; anchor lines; and swathing bands to bind prey.
The precise form of the filaments is deter¬mined by spinnerets—clusters of tiny nozzled jets from which the spider draws the silk with its hindmost pair of legs. The resulting strands of spider silk are incredibly elastic and tough—some can stretch more than 20 percent and are stronger than steel wire of the same diameter!
For all its beauty and dewy sparkle, the spider web is a diabolical achievement. To be sure, heavy insects like beetles and wasps, blundering into the snare, are apt to rip right through. But for lighter prey, the sticky, almost invisible network means death.
When delicate touch receptors pick up the slightest impact of an insect on the web, the spider skims across it to paralyze the victim with a single bite and binds it with silk (page 191). The hapless insect will either be eaten summarily—the body sucked dry of its nutritious fluids, the remains discarded—or left hanging in its mummy like wrapping for a future meal. In his classic work The Life of the Spider, J. Henri Fabre puts words into the mouth of a simple garden spider, “We must eat to have silk,” the spider exclaims, “we must have silk to eat….”
Instinct alone controls the weaving. But alter ever so slightly the spider’s internal chemistry, and the web will show it. I saw this demonstrated one morning in the laboratories of North Carolina’s Department of Mental Health, which experiments with spiders in one phase of a search for diagnostic clues to various mental illnesses payday loans direct lender.
Within an aluminum frame an orb weaver was performing a sequence of rapid runs, ascents, and descents. Tattered remnants of an earlier web stuck to one edge of the frame.
“Every morning we make her spin a new web,” said Mrs. Mabel Scarboro, a research assistant. “In the wild, a web seldom lasts more than a day or so; it’s ripped by wind, or insects, or even the movement of the spider itself. Even though we feed this one, her instinct tells her to keep her web in good repair or she’ll starve.”
In half an hour a completed web filled the frame. It was a circular marvel of straight lines, angles, and more than 800 individual attachments, all engineered with mathematical precision.
Another spider of the same species was busy spinning in a duplicate frame alongside. Earlier, this spider had demonstrated its ability to weave a regular, symmetrical web. But now it had been fed a droplet of sugar water containing “speed”—dexedrine sulphate.
Mrs. Scarboro sprayed the two webs with quick-drying white paint to make the threads stand out clearly. Then I saw the strange angles and illogical backtrackings in the weaving of the drugged spider. Laboratory measurements would record angles, affixment points, number of spokes, and other data for computer analysis.
Experimenters have found that different drugs—caffeine, mescaline, and LSD, for example—produce characteristic variations in a spider’s web. Some human mental illnesses seem to be accompanied by biochemical changes in the blood or tissue fluids. Could such fluids, ad-ministered to a spider, measurably influence its weaving patterns? If so, spiders might perhaps be able to tell us—through the varying patterns of their webs—the particular illness affecting a patient, or even his progress under psychiatric treatment. This is only one potential of the experiments, which are still in exploratory stages.