How Many Legs Does a Spider Have?

Every spider has exactly 8 legs, arranged in 4 pairs. This is one of the defining features of arachnids, the class that includes spiders, scorpions, ticks, and mites. Insects have 6 legs. Crustaceans have 10 or more. If something has 8 legs, it is almost certainly an arachnid. No exceptions in over 45,000 known spider species.

Each leg has 7 segments (coxa, trochanter, femur, patella, tibia, metatarsus, tarsus) and ends in tiny claws. Spiders do not have muscles to extend their legs. Instead they use hydraulic pressure: they pump fluid into the legs to straighten them and use muscles only to bend them back. This is why dead spiders always curl up. The hydraulic system depressurizes and the muscles pull the legs inward with nothing pushing back. It is also why spiders sometimes seem to "explode" in speed: the hydraulic system can extend legs faster than muscles alone could.

If a spider loses a leg, it can often regenerate it during its next molt. Young spiders molt frequently and can regrow a full leg in one or two molts. Adult spiders molt less often (some large tarantulas only once a year), so a lost leg takes longer to replace. A spider missing one or two legs can still function normally. Researchers have found that spiders missing legs adjust their gait pattern to compensate, similar to how a person with a limp shifts weight to the other side.

What each pair of legs does

8 legs vs 6 legs vs more

A common misconception: daddy longlegs (harvestmen) look like spiders and have 8 legs, but they are a separate order of arachnids (Opiliones), not true spiders. They have one body segment instead of two, and they cannot produce silk.

Spider records