The Insidious Trick That Helps Spiders Surprise Their Prey

Wow, it looks like Spider-Man really has been studying the battle tactics of a certain arachnid. By using high-speed film, scientists have learned that jumping spiders use silk draglines to balance themselves mid-air and make soft landings, in preparation for an attack.

Previously, scientists assumed that the silk lines merely provided jumping spiders with a safety line. But as new slow-motion footage reveals, the draglines also help them stabilize their bodies and brake for impact. This allows for soft landings — and to prepare them for a sneaky, predatory attack.

This makes sense. Other animals make soft landings by using the inertia from swinging appendages or through the flapping of wings. Jumping spiders, it now appears, do this with their silk lines.

Kai-jung Chi and colleagues analyzed the jumping ability of Adanson's house spider by filming their jumps at 1,000 frames per second. The researchers watched as the spiders used their draglines to control bodily orientation. Fascinatingly, the spiders were able to make super-fast adjustments to the dragline’s slack by controlling the valve in their spinning system.

"Without silk, upright-landing spiders would slip or even tumble, deferring completion of landing," write the researchers.

Indeed, the researchers also looked at non-silk jumping spiders, who typically lost their balance and tipped forward onto their backs after a precarious landing:

Intriguingly, the new insight could assist in the development of maneuverable robots.

Hmm, jumping robotic spiders. Sounds legit.

Read the entire study at the Royal Society journal, Interface: “More than a safety line: jump-stabilizing silk of salticids.”

Image: National Chung Hsing University.