How Do Spiders Make Webs?
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Spiders produce liquid silk in glands in the abdomen, extrude it through spinnerets where it hardens into thread, and build the structure through a fixed sequence of movements. The whole process is instinctive, and a spider gets it right on the first attempt without ever being shown.
It starts with the silk
Silk is produced as a liquid protein solution inside specialised glands. As it is drawn out through the spinnerets, the pulling force and changes in acidity cause the protein molecules to align and lock together into a solid fibre.
The change happens during extrusion rather than by drying, which is why a spider can produce thread on demand underwater or in humid air. Most orb weavers have several gland types producing different silks for different jobs.
Building an orb web
The construction sequence is consistent enough to describe step by step:
- •Release a fine thread into the breeze until it catches on something
- •Reinforce that first bridge line and build a frame around it
- •Lay radial spokes from the centre outwards, like wheel spokes
- •Spin a temporary non sticky spiral from the middle outwards as scaffolding
- •Replace it with the sticky capture spiral, working inwards and eating the temporary one
Why spiders do not stick
Only the capture spiral is coated in glue droplets. The radial spokes and frame are dry, and a spider moving around the web keeps to those lines.
There is more to it. Spider legs have a coating that reduces adhesion, fine hairs that minimise contact area, and careful movement that lets them peel off rather than pull straight away from a sticky thread. Spiders can and do get stuck occasionally, but the combination makes it rare.
How strong silk is
Dragline silk has a tensile strength comparable to high grade steel by weight, and it far outperforms steel in toughness, which measures how much energy it absorbs before breaking.
That toughness is the point. A web has to stop a flying insect without snapping or bouncing it back out, so the silk stretches, absorbs the impact and dissipates the energy. Materials scientists have spent decades trying to reproduce these properties artificially with only partial success.
Not all spiders build orbs
The classic wheel shaped orb is only one design among many. Sheet webs form horizontal platforms with tangled threads above that knock insects down onto them. Funnel webs have a retreat at the back where the spider waits.
Many spiders build no web at all. Jumping spiders stalk and pounce, using silk only as a safety line. Trapdoor spiders line a burrow and ambush from it. Even web builders use silk for egg sacs, wrapping prey and dispersing as spiderlings on strands carried by air currents.
Spiders on drugs and in space
In the 1940s and again in the 1990s, researchers gave spiders various substances and photographed the resulting webs. The results were used to argue that web geometry could serve as a sensitive measure of a compound's effect on the nervous system.
Spiders have also been flown to orbit several times. Early experiments produced messy webs, but later ones showed spiders adapting within days and building near normal webs, apparently using light as an orientation cue in the absence of gravity. Both lines of research use the web as a readable record of an animal's internal state, which few behaviours allow.
The takeaway
Spiders make webs by extruding liquid protein that solidifies as it is drawn out, following an instinctive construction sequence, and they avoid sticking by walking only on the dry radial threads with legs adapted to release easily.