How Many Legs Does a Spider Have?
Eight is the easy part. The catch is that eight legs alone does not make a spider: scorpions, harvestmen, ticks and even crabs all have eight. And the two pedipalps tucked beside a spider’s mouth look so much like a short fifth pair that plenty of people swear the answer is ten.
Count the legs, name the animal
Eight legs makes an arachnid — but not always a spider. Tap each to see.
Eight legs and two body segments — plus two pedipalps near the mouth that look like a short extra pair. That is the genuine article.
Silhouettes are representational. Leg counts are for a typical adult.
Advertisement
AdSense Slot: content_top
Eight legs: the whole identity test
All spiders belong to the class Arachnida, and four pairs of walking legs is the trait that defines it. That is why leg-counting is the fastest field test there is: if it has six legs, it is an insect, full stop — insects also carry antennae and often wings, which spiders never have.
A small twist most people miss: a spider’s legs extend hydraulically. Instead of a full set of extensor muscles, it pumps body fluid (haemolymph) to straighten the joints — which is why a dead spider curls up, with no pressure left to hold the legs out.
But eight legs is not enough to be a spider
This is where confident answers go wrong. Harvestmen, scorpions, mites and ticks are all eight-legged arachnids that are not spiders, and crabs reach eight walking legs from a completely different branch of life. Eight legs gets you to “probably an arachnid,” not to “spider.”
What actually makes a spider (order Araneae) is the combination: eight legs, two clear body segments joined by a narrow waist, and silk-producing spinnerets. The harvestman fails on the body — one fused section, no silk — which is exactly why the “daddy long legs” question gets its own page below.
Advertisement
AdSense Slot: content_bottom
The two legs that aren’t legs
Right at the front, beside the fangs, sit two short appendages called pedipalps. They look like a stubby extra pair of legs, which is the source of the “spiders have ten legs” mistake. They are not for walking: a spider uses them to feel its way and manipulate prey, and in adult males they are swollen into the organs used to transfer sperm during mating — the easiest way to sex a spider at a glance.
More spider answers
Sources
- Australian Museum & Natural History Museum (London) — spiders are arachnids with eight legs and two body segments; insects have six.
- Burke Museum (University of Washington), Spider Myths — harvestmen and other eight-legged arachnids are not spiders.
- BBC Science Focus — spider legs extend by hydraulic blood pressure, not extensor muscles, so dead spiders curl up.
- Pedipalps function in sensing, prey handling and (in males) mating — standard arachnology references.
Frequently asked questions
Related
Eight legs answers the question — but it is the two that aren’t legs, and the body behind them, that decide whether you are actually looking at a spider.