"Spiders are unique because they spin silk for so many different ecological functions," said Todd Blackledge, assistant professor of biology at the University of Akron in Ohio. "This has resulted in the evolution of a diverse toolkit of silks. We are discovering that these silks have a variety of physical properties and underlying genetic structures."
Blackledge and colleagues Adam Summers and Cheryl Hayashi decided to focus on black widow silks because the poisonous spiders construct a "very typical" cobweb.
Black widows are near the base of the evolutionary tree for the cobweb-weaving spider family Theridiidae.
The spider's large size and prevalence in certain parts of the country also made it a prime candidate for the study, published earlier this year in the journal Zoology.
According to the journal paper, black widows use a steel-like silk covered in a torturous glue to snare their prey. They then lasso and bind the prey in with a more spring-like silk.
The super-strong dragline silk makes up the supporting frame and radii of their webs. This same silk is coated with droplets of glue to make "gumfoots," or lines of web that are attached to the ground.
Prey insects minding their own business that get stuck on a gumfoot usually are goners.
"The gumfoot is attached to the ground in such a way that it easily breaks free from the ground when an insect sticks to the gluey foot portion," Blackledge told Animal Planet News. "The gumfoot is under a little tension so that it will actually lift insects into the air where they can't get a foothold to be able to struggle free."
The black widow likely then will subject the victim to the capture spiral, which is made of weaker, but more flexible, silk.
Like rope in a cowboy's lasso, the capture spiral silk can wrap around prey, now locked into the steel-strong web jail. Rendered powerless, the victim will be killed and eaten.
