UA biologist Dr. Todd Blackledge studies the web of a black widow spider. Blackledge and his research team discovered that starved black widow spiders build webs better equipped to capture prey than their satiated counterparts do.

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When hunger strikes a black widow spider, this arachnid spins into survival mode with a web chiefly designed to catch prey. University of Akron biologist Dr. Todd Blackledge and his research team discovered that starved black widow spiders build webs better equipped to capture prey than their satiated counterparts do.

Blackledge and fellow UA biologists Jacquelyn Zevenbergen and Nichole  Schneider revealed that hungry black widows spin webs with sticky gum-footed threads, which effectively entrap insects and alert the web inhabitant of the captured prey. Fed black widows, on the other hand, spin gauzy webs without sticky silk threads. The study, "Fine dining or fortress? Functional shifts in spider web architecture by the western black widow," appears in The Association for the Study of Animal Behaviour 2008, published by Elsevier Ltd. and available at www.sciencedirect.com.

"What we found was this really strange change in the architecture of the web, and that got us interested in trying to figure out what are the functional benefits of starved spiders spinning one type of web and fed spiders spinning a totally different looking web," says Blackledge, who studied 112 juvenile female black widows of similar size. Half of the spiders, those larger in proportion, received no prey for seven days prior to the experiment and the other half (56 smaller spiders) each received a small cricket every one of the seven days before the experiment.

Sticky vs. nonsticky threads

The starved black widows spun webs consisting of sheets of silk threads suspended by a series of sticky supporting threads coated at the base with glue and held under tension. The sticky silk thread restrained the prey and sent a vibration to the resident black widow, alerting it to mealtime. Meanwhile, the sated black widows produced nonsticky, tangle-based webs, which better serve to protect web inhabitants against predators than to catch prey.  Blackledge's research reveals that spiders (whether fed or starved) that hunted on sheet-based webs captured at least one prey more often than the same type of spider on a tangle-based web built by a fed spider.

"This research is more about animals and how they survive and live," Blackledge explains. "Spiders in different physiological states may alter the way they are producing silk, with more or less desirable properties, and that might tell us something about how the silk is assembled within the spider. That ‘something' is important for us to learn how to mimic that process. Fiber scientists face two challenges: understanding what those proteins within the spider are, and what the raw material really is."

Blackledge says scientists can dissect liquid protein from a spider, but can spin it at only about 10 percent the performance rate of a spider. Blackledge is studying both the structural properties of spider-spun silk and mechanical aspects of web building. He points out that one spider can spin seven types of silk that are mechanically and chemically different. Considering that there are more than 40,000 species of spiders spinning different types of webs opens significant possibilities to develop methodologies for enhancing the production of synthetic silk materials.