he earth is literally crawling with But in recent years this view has come spiders. Some 30,000 species have in for considerable revision. New breeds been tallied to date, and the guess is of arachnologists have emerged—arach- that half as many more still await nologist-cum-behaviorist and arach- discovery.■ Yet, despite their abundance nologist-cum-ecologist—specialists con­ and their ubiquity, spiders—members of a cerned with what spiders do, and where class of organisms called arachnids that, and how. And out of this pair of new also includes ticks, mites, scorpions and research foci, among others, is coming f M H H daddy longlegs—were long presumed to evidence that has all but demolished the be little more than evolutionary relics. supposition of spider irrelevance. Far The prevailing notion was that spiders from being trivial, spiders are now were ecologically irrelevant, vestigial believed not only to be critical con­ threads in the web of life. tributors to the balance of countless the Top "When researchers looked in the past," terrestrial ecosystems but to be a says arachnid ecologist Susan Riechert of superlative form of invertebrate life on the University of Tennessee, "they con­ earth as well. To Peter N. Witt, a 30-year cluded that spiders were ineffective veteran of spider investigation, the com­ Arachilia ” regulators of the insect populations plexity of spiders' neurally programmed because they failed to increase their own behavior, as reflected in the orb or numbers in response to increasing prey cartwheel web, is the ultimate expression populations,". With that verdict of in­ of superior, highly integrated in­ significance, it was hardly surprising that vertebrate brain function. arachnologists studying the spider king­ Not all spiders build webs. Of the 30 to dom traditionally confined their pursuits 50 families known, perhaps' half don't. largely to the realm of systematics or Many are insect trackers, vagrant preda­ Spider experiments. Behaviorist Peter M. Witt, work­ ing with Araneus diadematus, finds that taxonomy, the business of identifying tors. One such, the tarantula, is the most, spider webschange with the spider's age and that creatures according to family, genus, primitive spider of all. Spiders, nonethe­ drugs have an impact. The web at the far right, reflect species, etc. Trifling significance was less, conjure in most minds the image of the influence, of amphetamines, is compared to the attached to research efforts inquiring into intricate webs. adjacent normal web. the biodynamics of spider behavior or Different species weave different kinds Peter Witt their role in ecological systems. of webs. But generally the architecture Social spiders.SShe Mexican groufpiolerant spiders-, Mallos g re galls (left)^|||s®en mássé in a laboratory web (top right). The weScompl#x spider, Metepelra spinipßs, build! orb webs (above) in close proximity tp'.®ih othert ABoximity grid (right), applied to other species as well as^spiders^uggesM prinCiples ability. J. W. ípi rgeés^^hn^ll^.ury

the spider never missed a day building. highly refined statistical techniques. Fits one of three basic blueprints: the important functions in the head]. In man, spirals. (Witt never seeks to stress spiders to Over the years Witt has gotten so good sheet web (a two-dimensional structure the number of nerve cells in the brain far Poor vision seems to go along with web death in his experiments. "I love these at identifying webs that, if any of his showing no symmetry, the threads outstrips that seen elsewhere in the spinning; spiders need their webs to creatures, and that would break my crisscrossing each other in apparently nervous system. In spiders, cephalization extend their sensory and capture range. charges moves from one part of the heart," he says.) helter-skelter fashion), the space web (a is even more concentrated than in man." To show the importance of the web to laboratory to another, he can tell at a Even among members of the same scattered, three-dimensional, multilevel Among spiders, orb webbers, of which spider survival, Witt performed a series of glance where it has taken up residence. He species—or the same litter—no two arrangement) or the geometric orb (the some 6,000 species are known, may have near-starvation studies on his research can also tell, just by looking, how old the spiders build to exactly the same orb familiar two-dimensional cartwheel). The the most highly developed brain function, favorite, Amneus diadema!us, the orb­ spider is; web cha rae te r is t ips are age design. "Each web is tike a person's face, ultimate web—the most material- and since the orb web is the most patterned, spinning corn spider commonly found in dependent. fingerprint or signature—unique," Witt labor-efficient and most effective in the most preprogammed expression of an New England and many parts of Europe. Of the 6,000 or so orb-web species that explains, having established this snaring prey—is the orb web, says Witt, a exquisitely exacting blueprint written in When deprived of food, A. diadematus does ha vie been identified, all, follow pretty singularity only after ten years of pains- behavioral scientist who heads the North the genes. not spin a smaller web as a means of much the same behavioral pattern: each :aking analysis of web construction. Carolina Department of Mental Health There is no generation-to-generation conserving its protein resources. ,Np;r builds a new web every day—a task that The task required the identification of Research in Raleigh. teaching of web spinning among spiders; does it build a larger-than-normal struc­ generally takes less than a half hour to 1,000 distinct points on the web (where A. newborn spiderlings don't see their ture as a last-ditch effort to increase complete. The silk for web manufacture Uadematus fuses thread to thread), Cephalization and economy parents. For it to survive, a spider must capture capability. Instead, in Witt's emanates from sp inn erets, valveiike measurement of thread angles and dis­ Web spinning, which calls for many spin a letter-perfect web from the outset. experiments, every morning A. dmianutus structures on the posterior portion of the ntegrated behavioral functions, bespeaks There is, however, some flex in the continued to build its web to exactly the tances between spirals, quantification of spider's abdomen. Most spiders can spin a highly developed central nervous sys­ program, some plasticity, as Witt dis­ same dimensions as it had prior to the shape (e.g., whether the web was longer several kinds and thicknesses of silk^ aii tem. In fact, if brain volume and neuronal covered when he took a spider out of ||s days of famine. To obtain the necessary :han wider and by how much), tallying of Rafiy a^eyén j||some cases. Not all of it density are keys, Witt contends, then web midway through eoi^truc^6Panimal species grow more it had left off. But it adapted to its own spun a full-size web, but with a wider 1 he development of a complex computer ping prey, for lining a burrow or shelter or mplex," Witt observes, "there is in- material depletion by finishing the web mesh. Only after six weeks of starvation 1 •rogram (which in itself took three years fer en(flosing egg sacs in cocoons. Í: a sed cephalization Iconcentration of with abnormally wide spacing between did web size begin to shrink. Even then 1o elaborate) and the application of some The spiders build their webs modularlv. web—not the next day, but 48 hours later. aerially, through a process called balloon­ man zoologist who was affectionately This was demonstrated by in ing. At the appropriate time, depending known as "the spider web man." Peters collaboration with David Peakall, a on atmospheric conditions, the now- was gager ft© make a movie about web biochemist, then at Cornell University. arachnophobic spiderlings each dangle a building. But he was stymied by the fact In their experiments, Peakall and Witt thread of silk for capture by the wind, and that his spiders built their webs at 4 A.M., fed A. diademalus radioactively tagged off they soar. Alighting wherever the when ambient light for filmmaking was alanine, the principal amino acid in web breeze deposits them, the spiders actively lacking. protein, prompting the spiders to weave a seek out sites to spin their first, flawless, Peters asked Witt to se.e iiT Ihe could "hot" web. The original spiders were then orb webs. (Ballooning is a treacherous come up with a drug that would shift web­ removed and "cold" spiders placed on the business, which probably explains why so building activity to a later, more conven­ hub in their stead. Forty-eight hours later many more eggs are produced by wind- ient time. Witt gave various stimulants the new spiders, having eaten the webs to scattered species than by species whose and sedatives a try. All failed to alter the which they had been moved, were spin­ spiderlings disperse along the ground.) time of construction, but they did elicit ning the ingested, radioactive alanine into ff spiders are such aggressive, some­ some unexpected behavioral changes. their own webs. The 24-hour delay means times cannibalistic loners, how do they Under drug influence, the spiders wove the spiders have a whole other supply of manage to mate? (To borrow an old punch strangely deranged webs. silk protein to get them through the next line: Very carefully!) Mating is a risky Discouraged, Peters forsook the film day's architectural chores. proposition for the male. If the female is ■project. By then, however, Witt had Most ¡¡¡»he energy required Tor web not receptive, she can do the male serious, become intrigued, pouncing on the idea of building is expended in the steps the even mortal injury. using webs as a laboratory model for spider takes in moving about, tying the Not surprisingly, the courtship may last testing and understanding the effects of pieces together. Thus, the entire energy hours or days. It begins weeks before full hallucinogens and Other drugs. And so investment—"step" energy plus new-silk maturity, when the male stops web spiders became a major avenue of Witt's synthesis—is very small, amounting to building and sets out to hunt for a female research pursuits. what the spider derives from one or two over wide distances. "Animal models are indispensable to flies. The rest of the spider's energy store Apparently the male can tell, from the the study of mental aberration. Animal goes to predation and reproduction. nature of the web, which female is models give us a chance to get our hands Loners mature. Once the male discovers a on some hard, objective measures," says potential mate, it fastens a safety Witt. "People are much too individualistic Like most spiders, orb spinners lead thread—literally a getaway line—to an and unpredictable, in their responses, so solitary lives. The spider builds the web anchorage outside the web. His escape the results [of observing humans] can for its own use and brooks no encroach­ route established, the male makes his often be confounding." For instance, Witt ment. "Anything that touches the web is presence and intentions known by drum­ found, the spider web offers a powerful treated aggressively, as prey," says Witt. ming on the web in a characteristic visual analog of hallucination, providing He demonstrates this by buÄmg, a pattern. Sometimes the male may even an effective means of screening agents for vibrating tuning fork against the web. bring a gift—an insect wrapped in silk, for their mind-distorting potential. The spider tenses and attacks. instance. These preliminary approaches A few years ago—upon reporting on his PflfBly life, among liter- fflláMIISve to be repeated many times, spider/drug experiments and publishing mates, is there any semblance of tolerance interrupted perhaps by the male swinging some striking photographs of the wild with each of the several thousand meshes among A. diademalus. Several hundred awá^Jft®íí|;, the web outopl the female's webs woven under the influence of LSD, the product of a specific, short behavior newborns, miniature editions M adults, potentiallft dangerous clutches. It is not amphetamines, marijuana and caffeine— sequence. The web. features a hub area emerge simultaneously from the mature known what makes a female receptive to Witt received a considerable amount of where the spider rests and lies in wait, its egg cocoon (placed by the mother weeks ppé Balppgl another or at one time or exposure in the world press. He still hears legs grasping the radial threads. An or months earlier a distance away from another. ¡Pheromones—scent signals— from individuals seeking help for their adhesive substance on the spiral enhances her own web). These spiderliggs almost are p m ^ gs^ ^ ssim aj^ ^ sa being in­ mentally troubled relatives. One mother prey capture. A fly snared by the spiral immediately begin to lay threau'as they vestigated. But cues to whats-more than recently wrote to ask if feeding spiders to sets up llbraipm® in the web, with H move. Within a few days, their combined whim is certain to be i>nvolved^§||piftifl a her schizophrenic daughter would help radials serving to signal the location and peregrinations have produced a sheetlike mystery. heft of the trapped prey. The spider must while lacking añfl *° 8et a«d, if so, which species were best. Wilt responds sym­ act quickly; a fly can unglue itself in two or apparent geometry, serves the spiderlings The behaviorist pathetically. He understands, of course, three seconds. Scrambling from its head­ as a communal web. For fhe last dozen years.f p l l has based t«fe?^^i® reaching out: i@r any possible quarters in the1 h « j the spider Im­ The spiderlings may collectively attack his spider laboratory at the state mental jremedyij'^^ matter teOftynoutlandish, his mobilizes its catch with paralyzing bites any smalljpiey |fea|)catches on the web hospital in Raleigh. Invariably, this ap- correspondents are really demonstrating or by wrapping its find with silk. (Spiders, and wräpifpd Intruder 1® silk. But atllMf Ipareni ^^^^^SM^; raises eyebrows. a H^Äfftate need any heater though they are predators, subsist on a early stage spiderlings won't feed on thlSr What, áÉBH&ifc is a trájÉ M gmfiilóiait- f ^ f d w t e h iftf lfee ib fcto respond. completely liquid diet. They use their captive; they live instead on the remaining pharmacologist and a practicing director mouthparts to lacerate their insect prey. folk supply in their abdcfmins. heaiithdoing in Social spiders Then enzymes from the midgut pour out Gradtaalls'Vylih each siñ®eed¡ng molt, arachin;@Ji^&? On closer inspection the Witt's clinical orientation has led him in over the torn tissue, producing a broth the spiders grow more aggressive toward connection is really no;t at all illogical and 'T*e©ep!ft féSj§s| t©>f exipaifedö the research; that can be sucked up into the stomach.) réadh other. th^Bird and last molt, is, irtCjäct, clinicJflga relevant. purview of his labora^ry so that now it Web building is a model of economy and some two or three weeks after hatching, began in 1948 when en^Sgds a »h®Ife ©fther kind of spider energy conservation. Orb spinners, for the tolerant" phase is finished. The ¡Witt, a í ÍIrHÍ pharmacologist at the species. This species jPa| Sfesffe“á¡a alto­ instance, actually eat their webs every spiderlings simultaneously get read¡yg¡3 University » Tubingen, was approached gether rare the spider night and use more than 90 percent of the disperse, leaving the communal web by Hans M. meters, 111 tqaitemmHMBB-- kingdom: sociability or group living. recycled silk in the construction of a new

14 MOSAIC November/December 1978 Much of the impetus for this line of more elaborate than the web of any What was it about the buzzing that set interdependent, self-perpetuating colo­ ■ inquiry came from the presence on the related solitary spider. The cooperative the spiders off? Burgess was able to show nial system." , research staff of J. Wesley Burgess, a effort also means that little energy is that M. gregalis's web does not have a "flat" Burgess contends that there are not f biologist-cum-behaviorist who, under expended by any one colony member. audio response; the web is not a faithful only species-specific solutions to the ; Witt's tutelage, made social spiders his. To Mexicans in the countryside around transmitter of all frequencies. Rather, it problem of living and hunting together, I special province. Guadalajara, M. gregalis is known as el acts as a highly selective signal processor, but general ones as well. The goal is to Of the 30,000 spider species known, mosquero, the fly killer; they commonly suppressing some, enhancing others. At derive a methodology for evaluating j only 33 show any signs of tolerant adopt the spider to help control the pesky vibrations between 40 and 500 hertz interactions among spiders that can be : communal behavior in adult life. But even fly population, draping their homes with (cycles per second), thei signals are applied to other life forms. "This way we among many of these ostensibly social web-covered branches that serve as a significantly amplified. Vibrations below can add to the knowledge of phylogenetic , types, certain qualifications are in order. natural flypaper. The spiders' usual 40 and above 500 hertz are rapidly development in sociality and a better ; Metepeira spinipes, for instance, constructs quarry, houseflies and blowflies, at 20 to attenuated. Not surprisingly, the buzzing understanding of the variety of ways t an orb web for solitary dwelling. But the 30 milligrams each, are considerably of the housefly produces a spectrum of cooperation is possible," Burgess says. Í orbs are commonly distributed as a larger, larger than the biggest adult M. gregalis vibrations in the web within the resonant His latest investigations seek to deter­ interconnecting, three-dimensional space female, which weighs between 2 and 10 frequency window between 40 and 500 m ine the various means (chemical, ' web, shared by many spiders. With each ■ milligrams; predation works because the vibrational, tactile) by which spiders in (spider on its own piece of the shared species fiiftacks its prey in large groups. In another set of experiments, Burgess the web actively communicate and • structure, M. spinipes coexist peacefully; of Burgess's main lines i f inquiry used an electronic generator to send pure cooperate in prey sharing, courting, j but it's an entirely different story should has been to determine how social spiders signals ranging from 10 to 100,000 hertz reproduction and the raising of offspring. * any individual step over the boundary have mah-agedS^j fsprate each other. through the web. Only in the 40- to 500- A recent observation is that the male has onto another's orb.. Thqügh almist anything else (Sac, apr cycle band was he able to elicit predatory an advertising routine when he is ready to But there- are six truly communal Bpopriate siz'e-í^even ' other spidersSjia behavior: the jerky turning and •the mate. He drums in a distinctive way on < species. Because they are Unrelated and fair game, M. gregalis Somehow is not straightline scramble toward the signal the web, alerting the entire web popula­ j live bri six different .continents, Witt aggressive toward its own kind. teouWey* tion. But only mature females heed the i believes, it is safe to assume that spiders The web as signal processor This narrow cueing window may also signal and approach. ,i "invented societal living six times over." Most recently, Burgess has been paying What accounts for the tolerance? What explain tolerance and w B I absence o f (Each of these social species inhabits intraspecific predation. According to' particular attention to a study of the enables them to distinguish each other ¿tropical and subtropical locales where Burgess, spiders moving around on the distribution of social spiders on the web: from prey? The answer lies in the web, 5 there is often an abundance of insect web do not generate vibrations within the how they separate themselves from each says Burgess. M. gregalis, like most web- (fodder. resonant band. other. If there is measurable, reproducible spinning spiders, has spoor vision, so For the longest time, social spiders were The attenuation of signal information spacing, he explains, then it must result vibrations along the silken threads are ¡all but ignored by investigators. A few outside the transmission window may from an active form of communication probably the principal means of informa­ papers were published at the turn of the serve another protective function, that of among the spiders. For these trials, tion transfer and the key to aggressive vs. pcentury, "the last decent one" in 1910, keeping the spiders away from dangerous Burgess sets up a camera to take time- jfolerant behavior. (according to Witt. Not for, another six creatures that might come into the web. lapse photos of the animals automatically. In one set of experiments, Burgess ¿decades was anything more seen in the For instance, the characteristic buzzing of The slides are then projected onto a grid in placed several kinds of prey in the web: (scientific journals about these unusual a web-trapped honeybee is above a kilo­ the laboratory and, from the resulting anesthetized houseflies, flies with im­ ¿species. But since their rediscovery in the coordinates, information is extracted on mobilized wings, small and large hertz. Such signals are quickly damped by (late nineteen-sixties,, when a paper distances, distribution patterns and ac­ cockroaches and normal flies. Nonbuzz­ the web, and no predatory behavior is •appeared on spider sociality written by tivity rates. The data are then processed ing prey were virtually ignored by the observed. Thus, the attenuation quite ¡Ernst Kullman of Cologne, an animal by a computer. Colony. If a single spider accidentally often provides a mechanism for blocking ■behaviorist, interest has stepped up con­ So far, Burgess's observations have touched or. came near such quiet prey, it approach to a creature that could do the siderably. confirmed that social spiders do indeed might approach and feed individually. But spiders lethal damage. Burgess, Witt's behaviorist associate, actively arrange themselves on the web. no group predation was evident. Unlike most solitary spiders, M. gregalis ¡has concentrated his studies chiefly on The spiders tend to cluster in units of Events were decidedly different, how­ does not use silk binding to immobilize its j Mallos gregal is, the gregarious spider, a three, expressed in terms of nearest and ever, when an experimentally untreated prey. Most web-building spiders, Burgess ¡Mexican .inhabitant that also thrives in next nearest neighbors. By contrast, tests •fly got stuck in the web. It respondM ift® its explains, will Wfd^^piAy items, conspe-fí •the laboratory in Raleigh. M. gregalis éifics and intruders, indiscrim- with solitary spiders showed them to ¡builds a large, permanent, central web ¡pfiftdicament S y buzzp^foudly. The respond to the presence of another spider buzzing abruptly changed: the spider inateljy! The more straightforward orien­ ■that continues to increase in size as young tation and attack pftiSiatS of M. gregti|jpg by getting even more solitary, moving as behavior. Typically, a number emerged members of the colony lay new thread, sharply limits the likelihood of aggression far away as possible from their neighbors. j Web inhabitants may number in the from the intén®:§i?í the j^mbis^Bwited Burgess has extended his spacing mea­ themselves by a series of jerky jumps and aÄOüg consjp^iges. •thousands. Multitiered, the web has an surement technique to an analysis of sped straight for the h a p le sa » . If ;fhe Studying sociability adhesive surface for prey capture, a aggregative behavior in rhesus monkeys, Ihpzzing stopped for a moment or the fly complex network of interior tunnels and To Burgess, the social spider serves asa schooling fish, swarms of gnats and managed to escape, the spiders stopped passageways and chambers in which eggs an excellent model for seeking fundamen­ eóeteóá~ches|Cgj dead in their tracks. They became active are stored and spiders rest. tal clues to very basic questions on tbe • Ultimately, this methodology will be again if the buzzing resumed. evolution of social behavior in all species.;-, ' applied to an investigation of human M. gregalis measures an average body The spiders attacked the prey as "Social spiders are a good place to look for aggregation in a varié® of such social length of five millimeters and weighs only group. This set the fly to buzzing all the apj|wd^s to the evolution of communal settings as schools, airports or hospital about one-twentieth as much as most more, causing s«gBSlÍB*.,-'sÉ^feest ini- living since wé ha ve no real biases'afflu'tS wards. One potential benefit—and this is orb-spinning spiders. By combining eluding immature spiderlings, to scramble them," he sag&BHjp^gpk represtplfs a of special interest to Witt—would be ipi labors, however, a colony of social spiders to the scene. Soon the prey disappeared succesSM tradSp between social con- apply such knowledge to the design of the is able to construct a web much larger and under a pile of feeding spiders. cessions and mutual benefits to form an optimum mental hospital ward. "We’ve •red to win because of web-site ecological advantage: species richness. In the case of A. aperta, the territory y. "Think of it as home-court That's important, since no one species includes more than just the web—a age," says Riechert; "the inhabi- could fully utilize all the available food (or relatively permanent sheet web that lasts iows better than the challenger regulate the full spectrum of insect weeks or months, with the spider adding iod the site is and what it's fighting species). In one prairie site, for instance, to it daily. A. aperta polices an area beyond itain.%'4f Riechert counted 307 different spider the perimeter of the web, intolerant of »mparing eight different A. aperta species in the same habitat. The implica­ incursion even—or especially—by any tions, Riechert found that web and conspecific. Riechert likens the web to a tion here, says Riechert, is that the high corral and the territory outside the web to ry size are a function of prey intra-specific competitive interactions and ility and habitat. Not unexpected- territorial disputes probably limit inter­ a ranch with fence :nes. (To complete the ere prey density is greatest, web specific competition among spider com­ analogy, there's also a "ranch house," a ;rritory size are smallest. For munities, thus allowing sizable niche funnel built into the web, where the A. :e, those A. aperta inhabiting an overlap. She is currently investigating in aperta positions itself.) rich orchard in southern Mexico greater detail the role of and relationships Dramatic confirmation of territoriality in territories a twentieth the size within spider communities made up of came from a series of experiments in >e maintained by A. aperta in a far many spider populations. which 16 A. aperta were compelled to build tod-abundant New Mexican lava To Riechert, the story comes down to¡ webs inside individual, regularly spaced this: It is the fairly constant density of | metal cylinders. The cylinders were set in atic conditions also play a role; individual spider species, plus the broad a screened-in area normally occupied by ry size increases with increasing species composition in any given habitat, just two spiders. Once the spiders es­ e and climatic severity of the site, that works to maximize the spider's role tablished their webs, Riechert removed Arachnid ecology. Dispersion irgest territories are maintained as insect buffer. It is not, as investigators j of Agelenppsis aperta (left) differs the cylinders. It wasn't long before time for prey capture is limited by once theorized, simply a matter of prey- j -In New Mexican desert/grässs*. territorial disputes erupted. Within 14 rature extremes. (Metabolic related shifts in spider density. land environment (top) and days, the number of spiders in the Arizona desert creek bed ses of A. aperta are most efficient at Basing her contention on these new} enclosed area had been reduced to two. «(bottom). The bottom web is seen ratures ranging from 21 to 35 observations, Riechert suggests that (The other 14 had been killed, since escape .from the side;, its funnel-dips-into s centigrade.) Given the same spiders can be adapted by man to serve as litter. A spacing experiment was impossible; normally, in true field e, A. aperta holds a larger territory natural controls in certain vulnerable i ’(above) disclosed A. aperta's circumstances lacking an artificial enclo­ thermally stressful lava bed than a areas. Ironically, chemical pesticides often (crowding intolerance. At right, sure, the subordinate spiders would Susan Riechert watches spider avorable grassland habitat, have been much more effective in dislodg- j generally clear out rather than engage in feggr^s,iv^nteracti%rns while hert concludes that web and ing the native spider population than in combat.) |m o n envliiiQnmeirM ^ ry size are fine tuned to prey destroying ravaging insects. Her idea will ¡ plndiitiffip'n south-Géitral New The results in many trials were the »ility minima over an average of six soon be put to its first experimental trial; f same, regardless of whether the crowded m years. Thus, in good times, when William Whitcomb, a zoologist at the Susan Riechert' spiders were fed to saturation, fed what density is high, A. aperta doesn't University of Florida in Gainesville, plans * 1 « they would probably get under natural d by diminishing territory size, to introduce spider groups into an circumstances or held to starvation levels. designed wards arbitrarily/' says Witt, Riechert has been keeping tabs on step would allow more A. aperta to agricultural research station to see if the In all cases only two remained in a two- "without a shred of real scientific data several populations of Agelenopsis aperta, a ite the space and create future effort will help protect tall timber. spider-sized habitat. about how humans prefer to live spa­ solitary spider found predominantly in tition. Instead, it spends less time in In the Memoirs of Sherlock Holmes, Sir ; In the natural habitat, A. aperta actively tially." desert and grassland habitats in the ipture. Come the bad times, then, Arthur Conan Doyle has his master seeks out the best web site. Riechert Southwestern United States and Mexico. ere will still be enough food to detective make these remarks as he The ecological net thinks they locate potential sites on the By carefully tracking spider movements, tee survival. examines the evidence in a new case: "We As interesting as are spiders' rela­ basis of air vibrations set off by flying she has succeeded in turning up the tionally, when conditions are fa- are suffering from a plethora of surmise, í tionships to each other, as revealed by insects. Such vibrations are thought to be "missing link" long presumed necessary ?, the spiders increase their output conjecture and hypothesis. The difficulty current behavioral research, they are also picked up by tarsal slit organs, eardrum­ before the spider could take its rightful i. Usually A. aperta females produce is to detach the framework of fact...from being shown to play an ecological role. like structures on the spiders' legs, and place in the ecological web: the near- 100 eggs per sac. If it gets more the embellishments of theorists and j? That they help to regulate an ecosystem's trichobothria, fine, sensory hairs running synchronous swing'in predator and prey it will lay more eggs. (In the reporters. Then, having established ^ insect population should not be at all along the end portion of the body. population sizes that reflects predator lory Riechert found that females, ourselves on this sound basis, it is || |r surprising. Nevertheless, biologists long In many instances, choice web sites are response to prey availability. And why abundance, would lay as many as duty to see what inference may be drawn , rejected this idea, holding to the belief limited, leaving many spiders without a had this putative link escaped detection egg sacs in a breeding season.) and what are the special points upon P that spiders are ineffective as natural pest good place to settle. Based on her observa­ for so long? Because, Riechert explains, i then; at last, was the long-sought which the whole mystery turns." controls. The reason was that, in studied tion of the movements of more than 200 spider population dynamics are subtle and ig link": More insects mean more ecosystems, spiders did not show any physically tagged A. aperta, Riechert esti­ To Peter Witt, who is fond of that easily misconstrued. They are masked by nd do indeed mean more spiders, population increase, the classical con­ mates that, at any given time, in any given Doyle quote, "Spiders have been much- a hitherto little-recognized behavioral lere was also a catch: Because of comitant of intensified predation, in habitat, at least five percent of the spider maligned victims of this 'plethora of | ■ attribute: fierce territoriality. riality, population size within a surmise'" in the absence of much hard and 1 response to increases in insect numbers in population is on the prowl for new sites. habitat would not show the ex- fast data about their true living habits. the same region. Or at least no such Territoriality As such, the likelihood of a spider density increase. The most fit But all that is changing now as a new response could be found. "We know that territorial behavior is encroaching on an already occupied web lin established territories . in the breed of arachnologists takes to looking at It was a paradox, but without evidence common among vertebrates,'^ says site is very high. Often, a newcomer will 3t sites; others leav^flthe habitat/ the "special points upon which the whole to the contrary, spiders had to be classed Riechert. "It's not nearly so well recog­ seek to oust the occupant. Generally, the to build webs on the less desirable spoils—the web and the territory—go to mystery turns." • as an ecological sport. That the spider is nized among invertebrates. But.it's there rts, enlarging the range in the all right. In fact, it's widespread, but has the heavier of the two combatants. In now being recognized as integral to s. The National Science Foundation contributes to the ecological systems is largely the conse­ largely been overlooked because in­ most instances, the battle is more feints hert suggests that this well- support of research reported in this article through quence *of research conducted by vertebrates often employ subtle methods and bluffs than actual fighting. When the ted territoriality provides another its Psychobiology and Ecology Programs. Tennessee's Susan Riechert. of territorial maintenance." differences in size are small, the resident