Nice Threads

While you're hanging decorations this Halloween, take a moment to marvel at the wonder that is the spiderweb. Classic circular or orb webs are actually constructed from up to five different types of silk, each serving a particular function. Evolutionary biologist and arachnologist Catherine Craig, '73, and co-author Leslie Brunetta explore how spiders developed this specialized toolset in Spider Silk: Evolution and 400 Million Years of Spinning, Waiting, Snagging and Mating (Yale University Press).

Strongest: Though only a few microns in diameter, major-ampullate, or dragline, silk is stronger per unit weight than steel. Spiders release it as a safety tether when rappelling and use it to frame their webs.

Stretchiest: Flagelliform, or capture spiral, silk can extend to more than double its original length without breaking. Orb-weaving spiders use it for the "bullseye" center of their webs to snare fast-moving prey.

Toughest: Aciniform silk can absorb two to three times the amount of kinetic energy without shearing as other silks, including dragline. Spiders use it to wrap up freshly captured—and often still struggling—prey.

Stickiest: Considered to be the most effective biological glue, liquid aggregate silk often appears as glittering droplets decorating a web. These viscous beads attract prey and hold them fast.