Spider Mystery Solved

http://www.tpwmagazine.com/archive/2008/jan/ed_2/

I enjoy camping out by the lakes but although I appreciate this phenomenom as a scientific curiosity, my personal curiosity is not stirred sufficiently to entice me to view it. I don't like spiders and have no desire to get close to such a population explosion of them. Brrr! Gives me the shudders to think of it. The Old Woman (Worried American) is fairly tolerant of spiders and was curious about this explosion when the news first broke. she didn't make the drive to view it. I have noted that her spider tolerance has limits, however. Once when we were returning from Corpus Christi and crossed a bridge over a body of water, she spotted thick stands of the pest water hyacinth growing at the water's edge. She wanted a few specimens to float in one of her patio fountain bowls so waded through the knee high weeds to get some. Once there, she finally noted that practically every weed sported a web of a baby golden orb weaver spiderling, a spider of which she is NOT fond. Damn! I didn't know the old woman could move so fast -- uphill, too! She tore it up getting back to the car, without the water hyacinths. :)
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http://texasento.net/Social_Spider.htm
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http://www.tpwmagazine.com/archive/2008/jan/ed_2/

January 2008

Web Mania!

Spiders spin a mysterious masterpiece at Lake Tawakoni - and ignite a media frenzy.

By Sheryl Smith-Rodgers

As soon as the news made headlines across Texas - and around the globe - I fired off an e-mail: I want this assignment! Though sent as a joke, I was serious, too. Imagine my surprise when I read the reply: Hightail it up there! The next morning, long before sunrise, I jumped in my car and hurried north to Lake Tawakoni State Park east of Dallas, where massive amounts of spiderwebs enshrouded trees and other vegetation on a remote hiking trail.

Along the way, I followed Mike Quinn, an invertebrate biologist with the Texas Parks and Wildlife Department, who'd been watching the webs via online photos. He wanted to look at the scene firsthand and collect specimens. Like other biologists and arachnologists, he was baffled. Had scores of spiderlings tried to disperse? Or had social spiders taken up residence in the park? Why had so many spiders - which by nature are normally solitary - congregated in one area? What species would he find?

As for myself, I couldn't wait to see the web. Spiders have long fascinated me. Several years ago, I bought a plethora of spider books and read all I could. I'd kept an assortment of live spiders, raised three tarantula spiderlings and shared my passion with anyone who'd listen. Today - the last day of August - I would witness a genuine spider phenomenon that had the whole world talking.

Remarkable discovery

No one's quite sure when construction began on the park's giant web. But Kim Feuerbacher of Rockwall and her son Trent saw something in early summer. While biking on a trail on the park's north side, they braked when they came upon thousands of silvery strands, strung high and glistening in several post oaks. "It was beautiful, but we couldn't get off that trail fast enough!" recalls Feuerbacher, who mentioned what they'd seen only to her husband.

In the following weeks, endless rains and muddy conditions kept most visitors off the trails. Finally, a dry spell came August 6, which meant park ranger Freddie Gowin could get back on a mower. While on a nature trail, he rounded a curve, then gaped dumbfounded. "The web was plumb across the trail and all over the trees!" he says. "I had to drive through it to finish mowing."

Nine days later, superintendent Donna Garde photographed what she called a "white fairyland" of gossamer that enveloped six trees, underlying vegetation and the ground. The photos were e-mailed August 24 to TPWD biologist Mike Quinn and other entomologists. Stunned and befuddled, he forwarded the startling images to several more spider experts across the nation.

Reponses boomeranged back. Some speculated that the web belonged to a social cobweb spider (Anelosimus studiosus) known to coexist in colonies, where females cooperatively capture prey and care for young. Others theorized that spiderlings had attempted a "mass dispersal," behavior associated with "ballooning" (when spiderlings release strands of silk into the air and float away to a new location).

Meanwhile, news of the web broke August 29 in the Fort Worth Star-Telegram. Quickly, other print and broadcast media from across the country - and around the world - jumped on the story. Reporters as well as curious visitors streamed into the park; staff fielded relentless inquiries by phone. Over Labor Day weekend, more than 3,300 people hiked the trail to see the web, damaged by recent rains but still active with spiders.

Spiders collected

The media frenzy had slowed only slightly by the time Mike Quinn and I arrived Friday, August 31. A newspaper reporter who'd made the quarter-mile trek (one way) numerous times led the way. He escorted us down the dirt trail, which cut across a small grassy prairie, then through thick woods. The path continued across a clearing; from there, we could see Lake Tawakoni. We rounded a clump of shrubs, then joined a small group of people standing beneath an eerie canopy. Around us, foliage drooped beneath dark gauze littered with debris and bug bodies. Brown and deteriorated, some long, thick webs hung like Spanish moss. Sunshine filtered through holes and tears in the webs, casting a hazy light on the strange scene.

Beneath hackberries, junipers and post oaks that reached at least 25 feet high, more webs covered saplings, vines, grass and fallen limbs. The musty odor of decay permeated the hot, humid air. "This is like nothing I've seen before!" Quinn declared. Then he and Joe Lapp, a spider enthusiast from Austin, examined web after web, identifying spiders and insects as they worked. "The predominant species is definitely a long-jawed orbweaver," Quinn concluded.

Indeed, countless numbers of tetragnathids - a long-legged spider with an elongated body - clustered within inches of one another in the dense webs. I looked up and saw more on loose, tangled webs strung high between branches and from tree to tree. Many were folded in a characteristic lengthwise position, their bodies silhouetted against the blue sky.

Typically, tetragnathids singularly spin and catch prey in round "orb" webs, often built horizontally near water and in close proximity to other long-jawed orbweavers. As its name suggests, this species has a long pair of jaws (chelicerae) equipped with fangs that inject venom to paralyze insects. (Only the venom of black widows and brown recluses is harmful - but not fatal - to humans.)

At Lake Tawakoni, though, tetragnathids had changed their behavior. Very few had built normal orb webs. Why? Experts would later try to answer that question and more.

"There's certainly a lot of food here," Lapp observed as he peered at one tangled web.

"Look, that jumping spider got a cricket!" Everywhere, carcasses of grasshoppers, mosquitoes, gnat-like midges and other insects - including live ones and dead spiders, too - stuck to the webs. Excessive rains had evidently caused an explosion in mosquito and midge populations.

Other spiders inhabited the area, too. In some poison ivy, I spotted a female wolf spider carrying a mass of tiny spiderlings on her back. Within a jungle of high weeds, a yellow garden spider hung upside down on her orb web. Tubular-shaped webs on tree limbs indicated the presence of funnel weaver spiders. Numerous species of jumping spiders - which stalk their prey like a cat - lurked nearly everywhere.

Experts weigh in

After several hours, I headed home, exhausted. Quinn and Lapp, though, stayed until well past dark, collecting spiders and observing their behavior. On Saturday, Quinn delivered 250 specimens to Allen Dean, a research assistant in the Texas A&M University Insect Collection. Dean, who specializes in spider taxonomy, spent most of the next day analyzing spiders under a microscope. His findings: tetragnathids - specifically Tetragnatha guatemalensis - comprised 60 percent of the sampling. Jumping spiders accounted for 18.4 percent and orbweavers, 7.6 percent. In all, Dean identified 12 different families and at least 16 genera.

"Since the world was waiting to find out what spiders were there, I took my time because I had to be certain of the identifications," says Dean, who later visited the webs in September. "Once you release a list, you can't make corrections." By Monday (Labor Day), Garde had hard data to share with reporters and visitors alike.

Solving the mystery

Bolstered by the identifications and activity reports from the site, experts could better explain Lake Tawakoni's giant web. According to John Jackman, professor and extension entomology specialist at Texas A&M, a bumper crop of bugs can trigger massive webbing and even affect spider behavior.

"It seems to be documented in the literature that if you have an abundance of food, spiders throw out additional webbing and even crawl into each other's webs," says Jackman, author of A Field Guide to Spiders and Scorpions of Texas. "Then they just sit there and eat the abundant food, so they're not regulating each other by feeding on spiders. We've had other reports similar to this, and they seem to occur near a lake or a light."

Norman Horner, emeritus biology professor and spider expert at Midwestern State University, visited the state park September 14 with assistant biology professor Roy Vogtsberger. Like Jackman, Horner believes that food plays a key role in understanding spider dynamics at Lake Tawakoni.

First of all, ample food at the start of a spider's life cycle can lead to higher spider numbers. That's because females lay hundreds of eggs within a sac, but only a few survive, Horner says. In nature, they're eaten by one another or by larger spiders and other predators. If there are more food sources to go around, then more spiderlings survive and molt into adults (spiders "grow" by shedding their hard exoskeletons).

High survival rates coupled with still abundant food kept long-jawed orbweavers (and other species) busily spinning at Lake Tawakoni. "Normally, tetragnathids are a solitary spider that will get in close association to one another but not share a web," Horner says.

"Spiders will feed on one another, even if they're the same species. But we didn't notice any cannibalism there at all. Based on what I saw, these tetragnathids have moved from a solitary existence into a semi-social communal web."

Another observation: "Interestingly enough, it appeared that the spiders at the state park were not using the webs to trap prey but to grab it as it came by," Horner says.

Worldwide attention

Quinn - who posted and regularly updated a Web site on the giant spiderweb - was not only intrigued by the rare phenomenon but also how the story and related photographs fascinated the entire world. Media called and e-mailed from Australia, England, Norway, Germany, China and even the Middle East. American markets ranged from Time, Today Show, CNN and National Public Radio to Ranger Rick, Scholastic News and Martha Stewart's TV show. On the New York Times Web site (August 31), the Texas web ranked "number one e-mailed story of the day."

In subsequent weeks, other researchers, too, spent long hours at Lake Tawakoni. Though the spiders and web have since died off, forthcoming documentary programs, scientific papers and magazine articles will keep interest stirred. "I love how this is bringing a lot more data into the scientific community," Garde says. "And the publicity for our park has been incredible."

How unique was the Texas web?

"That was a big question people asked," Quinn reflects. "The fact that the story went wall to wall (around the world) and few reports came back on similar occurrences, well, that says something!"

As for the future, "It will be interesting to see what happens next summer," Horner muses. "Nature has a way of bringing things back in line."

Epilogue

The saga continued October 1 when reports came of similar webs spread across trees at Wind Point Park across Lake Tawakoni. While surveying the state park site that day, Joe Lapp and Hank Guarisco (adjunct curator of arachnids at the Sternberg Museum of Natural History at Fort Hays State University in Hays, Kansas) drove to the privately owned park. There they found mostly long-jawed orbweavers but also social cobweb spiders, too.

Three days later, Lapp confirmed another large tetragnathid web - this one near Lake Travis. For a detailed timeline, and ongoing updates, visit texasento.net/Social_Spider.htm. For more information about this web and similar webs around Texas, see a multimedia journal at Joe Lapp's Web site, www.SpiderJoe.com.

On the Night Watch

Spiders became more aggressive - even cannibalistic - after dark.

I spent about 10 days camping in Lake Tawakoni State Park during September and October, observing the giant web and its resident spiders. The main actor in this somewhat surrealistic arachnid play was a species of long-jawed spider (Tetragnatha guatemalensis), which was often found in great numbers resting in the web during the day.

Although I saw mating and prey capture during the day, the real action on the giant spiderweb began after the sun went down. After dark, three supporting actors - other species of orbweaving spiders that remained hidden while resting in the vegetation during the day (Larinioides cornutus, Metazygia wittfeldae and Neoscona crucifera) - came on stage and joined in the hurried web-building activity of the female long-jawed spiders. Each spider built a circular orb web to catch the hordes of small flies that rose into the trees after sunset. Space was limited, so the spiders attached their webs to any available structure, including their neighbors' webs. Under normal conditions, they are very protective of their personal space, but with the almost unlimited food supply, they became much more tolerant of one another.

As male long-jawed spiders wandered in search of food and females, they frequently invaded the outer edges of newly constructed orbs without triggering aggressive reactions from their owners, which were usually too busy eating to mind the disturbance. As food became scarcer, however, this arachnid play took a darker turn. The densely packed long-jawed spiders became very aggressive and scenes of cannibalism became commonplace on the giant web. Females attacked other females, males and juveniles. Spiders became an important part of their diet at this stage.

One of the three supporting actors (Neoscona crucifera) was responsible for some of the large silk streamers suspended among the trees. This spider built large orb webs in open spaces between trees that are often 15 to 20 feet apart. Before sunrise, the spider ate its own orb web but left the framework of silk suspended between the trees. Long-jawed spiders and others traveled across this silken "super highway," laying down their own dragline silk as they went. Eventually, the heavy traffic created a wide silk band between the trees.

- Hank Guarisco