Why Don't Spiders Stick to Their Own Webs? Silk Secrets

Most of the web is not sticky

An orb web is built from several kinds of silk, and only one of them is sticky. The frame, the straight spokes (radii) and the hub are made of dry silk. The sticky thread is the capture spiral, coated with tiny droplets of glue, which winds around between the spokes. You can see how these parts are added one by one in how spiders spin webs.

When an orb weaver runs to prey, it travels mostly along the dry spokes like a person using the rungs of a ladder. Near the hub, many spiders leave a free zone with no sticky spiral at all, so the place where they rest and turn around is completely dry. The European garden spider often waits at this hub or in a hideout at the edge of the web, connected by a dry signal line.

Clawed feet that barely touch the silk

A web-building spider’s foot ends in three claws: two comb-like claws and a smaller middle hook. Next to them are stiff, toothed bristles. To grip a thread, the spider pulls it over the middle claw and presses it against these bristles. To let go, it relaxes, and the thread springs free.

This system means the spider holds a thread with only a tiny contact area, instead of standing on it with the flat underside of its foot. Watching a spider closely, you can see that it hooks threads with its leg tips and moves deliberately, rather than planting its legs onto the silk.

Hairy legs with a non-stick coating

Spiders cannot avoid the sticky spiral entirely. While building the capture spiral, an orb weaver repeatedly touches the fresh glue with its legs. A 2012 study of the golden silk orb weaver found three tricks working together:

• Careful movements. The spider touches sticky threads briefly and lightly with its leg tips, often using just a few points of contact.
• Branched hairs. The legs are densely covered with hairs, some branched at the tip, which hold the glue droplets away from the leg surface and reduce how much glue touches the leg.
• A chemical non-stick surface. When the researchers washed the spiders’ legs with a solvent, the legs became much stickier, showing that the surface carries a coating that resists the glue.

The old explanation that spiders have “oily feet” is a simplification. No oil glands have been found on spider legs, but the non-stick surface layer plays a similar role.

What makes the capture spiral so sticky?

The glue on an orb web is made in special glands and laid down as a coating that soon beads up into evenly spaced droplets, like dew on a string. Each droplet contains sticky glycoproteins and a mix of compounds that attract water from the air, keeping the glue soft and tacky.

The glue is especially good at sticking to the waxy outer surface of insects, and it spreads out over an insect’s body on contact. At the same time, the thread underneath is very stretchy, so a struggling insect stretches the thread instead of breaking free. The silk types behind this are explained in how spiders make silk.

Not all spiders use glue. Some web builders comb out an extremely fine woolly silk, called cribellate silk, which entangles insect bristles and holds them without any liquid glue.

Do spiders ever get stuck?

Yes, sometimes. A spider that is knocked off balance or lands hard on the sticky spiral can get a leg caught. It usually frees itself by pulling carefully or by cutting the thread. Afterward spiders often clean their legs by drawing them through their mouthparts, removing glue and dirt.

Spiders are also not immune to other spiders’ webs. Small spiders are regularly caught and eaten in the webs of larger ones. Pirate spiders take advantage of this: they enter another spider’s web, pluck the threads to imitate trapped prey, and attack the owner when it arrives. Other small spiders live as thieves in big orb webs, stealing tiny insects the owner ignores.

Why it matters

Being able to move freely across a sticky trap is essential to the orb weaver’s way of life. A spider that stuck to its own glue could not build its web, reach its prey quickly, or escape from birds and wasps. The combination of dry threads, clever feet and non-stick legs lets spiders use one of the most effective prey traps in nature, catching the insects that make up most of what spiders eat.