They also took digital images, which they used to perform similar strength tests virtually using a computer software program.
The researchers then compared the resulting data with 276 capture spiral webs taken from several orb-weaving spiders that are common to gardens in the southwest, where the study was conducted.
Blackledge and his team determined that the windlasses and the glue did not contribute much to the capture silk's flexibility or to the dragline silk's toughness. Instead, they now believe the differences between the silks are due to the fibers' underlying amino acids.
The secret to the strength of dragline silk, which probably could absorb the impact of a bullet if it could be woven into clothing, is that its amino acids join into tight crystals, which make the silk's protein fibers stiff and strong.
Capture silk, on the other hand, is made up of coiled protein chains that can spring, stretch and rebound.
"This offers exciting potential for the production of biomimetic fibers because we may ultimately be able to use our understanding of spider silks to individually engineer fibers for custom purposes," Blackledge said.
Randy Lewis, professor of molecular biology at the University of Wyoming, who has previously speculated about silk proteins, said he and his colleagues "are in complete agreement with the conclusions from (the Zoology paper) data."
Lewis, along with Blackledge, hopes black widow webs, and the silks secreted by other spiders, will inspire new manmade materials in future.
Name: Black Widow (
Latrodectus mactans)
Primary Classification: Theridiidae (Cobweb Weavers)
Location: United States, Canada, Mexico, the West Indies and South America.
Habitat: Temperate grassland, chaparral and desert in temperate and tropical zones.
Diet: Mainly insects. Also wood lice, millipedes, centipedes and other spiders.
Size: Females are 0.3 to 0.4 inches in length. Males are 0.1 to 0.15 inches in length.
Description: Shiny, coal black in color; female has long, slender legs, a round abdomen, a red hourglass mark on the abdome and red spots over spinnerets and along back; male has elongated abdomen, large legs, orange-brown joints and red and white stripes on sides of abdomen.
Cool Facts: The female's coarse, funnel-shaped web has three structural levels: an uppermost complex of supporting threads, a central zone of tangle threads and a lower zone of vertical trap threads. The female will eat the male if he doesn't play the right tune on her web during courting, or immediately after mating.
Conservation Status: Common
