Spiders and the Cobwebs of Myth about Them Number 31 August 1, 1983 LayPeople often wonder why their tax spiders, could find “no obvious justifica- dollars should support science that tion for so dkproportionate, so wide- seems to have no relevance to everyday spread, so illogical a horror, which may problems. Why, for example, should welf have been an obstacle to serious they give money to people to study arachnology. ”1 Savory believed that the spiders or scorpions? What makes fear of spiders is complex and no single arachnology, the study of these crea- explanation can cover all cases. Like tures, relevant? The importance of many other phobias, however, it can arachnology became apparent to me often be traced to early chfldhood. Per- many years ago. As I lay on a mound haps a chdd, warned about poisonous during an Army maneuver in Texas, I and ferocious animals, transferred the felt a shooting pain move down my left fear to spiders. Or maybe the child was arm toward my chest. I thought I was once frightened by a spider. As Savory having a heart attack. It turned out to be notes, “Few creatures are more likely a scorpion sting. Many years later, I was than a house spider to appear unexpect- reminded of the relevance of arachnol- edly and give a shock to a child.”1 ogy while living on an asparagus farm Anthropologist Marvin Harris, Uni- with my son in New Jersey. A small child versit y of Florida, Gainesville, agrees was bitten by a black widow spider in an that the fear is learned in childhood. outhouse. Fortunately, the child sur- Since some spiders can be dangerous, he vived. says, it makes “good cultural sense” to Apart from the relevance of such ob- teach chddren to stay away from them. scure subjects as arachnology, scientists The fear need not be permanent. Hu- have another problem. We seem to en- mans can learn to love spiders and let joy what we do too much. The average them walk on their arms without fear.z person can’t comprehend why anyone Edward O. Wilson, Harvard Univer- would enjoy working with all those sity, Cambridge, Massachusetts, be- “things” they fear most: spiders, iieves the phobia is rooted in our genes. corpses, diseases, etc. Scientists need to “Wh~le there is a strong predisposition to be reminded that our lay friends have develop phobias against spiders, snakes, not acquired the knowledge that over- closed places and cliffs-the ancient comes common myth and superstition. perils of humankind—there is no predis- Like snakes and wolves, spiders have re- position whatever to form phobias ceived a bum rap. Perhaps this essay will against knives, electric sockets and au- indicate why. tomobiles, which are far more danger- Few animals are more universally ous in modem society.”z feared than spiders, Why people fear Whatever the root of human fear of them has never been precisely ex- spiders, these creatures have held a cer- plained. The late Theodore H. Savory, a tain fascination as well. Spiders figure in British author of textbooks about ancient myths. In 8 AD, the Roman poet 237 Ovid told the story of Arachne, a peas- legs allow them to step quickly over rug- ant girl who challenged the goddess ged temain. Chitinous exoskeletons Athena to a weaving contest. The wom- make them unappetizing to many preda- en produced cloth of equal beauty, but tors. And venoms, in tiny amounts, par- the jealous Athena punished Arachne, alyze their insect prey. A spider caught changing her into a creature that spends by the leg can leave it behind and grow its liie weaving silk: a spiders another at next molt .s Thomas Eisner Spiders belong to the phylum Arthro- and Scott Camazine, Cornell University, pods, which they share with insects and Ithaca, New York, recently made an crustaceans.q Arachnida, the subdivi- amazing dkcovery. When a spider is sion or class of arthropods spiders belong stung in the leg by a venomous insect, to, is named after Arachne. It afso in- such as a wasp or honeybee, it lets go of cludes worpions, mites, and ticks. LAe the leg within seconds, before the venom most of their fellow arachnids, spiders spreads through its body,g are air-breathing invertebrates. Their In addition to these adaptations, the bodies have two ditilons, four pairs of spider’s use of sifk is one of its tools for legs, and no antennae.s Unlike other survival. According to F. Lucas, Shirley arachnids, all spiders spin silk, though Institute, a fiber-research organization not alf build webs.b in England, spider silk is stronger than Most spiders have eight eyes, though nylon. It is also finer, lighter, and more some species have fewer. Most spiders tenacious than silk from the common secrete venom, although only about silkworm, Bornbyx men”.lo All silks are 12 species are harmful to humans. Their made of a protein called fibroin. Spiders main diet is insects. They eat by first in- produce it in up to six sets of glands in jecting the victim with venom and treat- their abdomens. They secrete it through ing it with digestive enzymes that dis- valve-like openings, or spinnerets, solve its inner organs. Then they drink which help regulate the flow. 1I the resulting nutritive broth. Spiders Spiders’ silk is the basis for one of their hatch from eggs and change little as they most prominent survival tactics: the mature, except in size. They usually web. About half of all spider species molt (shed their chttinous outer skin) build them, Peter N. Witt, an arachnolo- seven or eight times before maturing. gist-pharrnacologist retired from the Females are often larger than males, and North Carolina Department of Human sometimes devour males after mating.b Resources, points out in a recent news There are about 35,000 known species story that webs are great energy savers of spiders.b Some scholars, including for spiders. Web-builders do not have to Norman 1. Platnick, American Museum roam in search of prey. They simply wait of Natural History, New York, befieve for insects to get caught in the web. that at least 100,000 species inhabh the Buildlng a web costs a spider the energy Earth.7 During the course of their 400 equivalent of two or three insects; on an million-year history, spiders have average day, a spider may catch 30. And adapted to almost every climate and many spiders recycle their webs, They every ecological niche, Accord~ng to eat all or part of the silk at the end of the Paul A. Zahl, National Geographic day and use its amino acids in their next Society, Washington, DC, they exist in web.lz great variety among the trees, bushes, According to Witt and colleagues, and grasses of every forest in the world. spiders build their webs according to in- Spiders are found from the tropics to the structions encoded in their genes. They Arctic. And some species, though they can build the day they hatch, though breathe air, live underwater.a most produce their fwst web after two Spiders clearly have efficient survival weeks, 13 W hlle each species spins a mechanisms, since they are so numerous characteristic web, individuals vary it in and widespread. Newly hatched spiders minor ways, making each web almost as are as mobile and fierce as adults. Eight distinctive as a fingerprint. And even 238 though a spiderling rarely gets to meet its field Hills, Michigan, thw modest maze parents, its web closely resembles of tangled threads is attached to sur- theirs. 12 rounding structures in a haphazard- Different species of spiders build dif- looking way. lb Although the cobweb is ferent webs which vary greatly in their considered a nuisance by people who en- degree of complexity, One of the struc- counter it, Anne Moreton, an amateur turally simpler webs is the single line web arachnologist from Powhaton, Vir~la, of the tropical spider l%oroncidia studo. has found that it helps the spider catch The web consists of a strand or two of more than 1,000 flies, mosquitoes, and silk stretched across a path or stream. moths a year. 17 Observing in a forest near Yotoco, A more ambitious web is called the Vane, Colombia, WMiam G. Eberhard, sheet web. It’s a thick plane of hundreds University of Costa Rica, Costa Rica, of fine silk filaments placed very close found that insects move more slowly together. Some spiders crawl atop the when flying near the web, and end up be- mesh. Others, such as Linyphia triangu- ing caught by their feet. He concluded lmis, hang from beneath with specially that thk flying pattern indicates the pres- adapted toothed claws. ThK spider ex- ence of a chemical attractant, or phero- tends thin filaments from the web to mone, in the silk, 14 structures high above it. Insects fly into Another simple web, the cobweb, is the filaments and fall onto the web sur- spun by the common house spider face, where the spider can pull them Achaemnea tepidariomm. The cobweb through from underneath. lb (See Figure gets its name from the Old Englishword 1.) cob, for spider. 15 According to a 1964 Some spiders, such as the 1,300 spe- book by Laura B. Lougee, then with the cies in the fam~les Dipluridae and Cranbrook Institute of Science, Bloom- Agelenidae, weave their snares into the F@ne 1t Linyphia trrhnguiaris hangs underneath its horimntal sheet web and pulls trapped prey through. (From: The Worfd of Spiders, Bi+stowe,WS, William Collins Sons& Co.