Spiders Don’t Jump With Muscles – They Use Blood Pressure

Spiders don’t use specialized leg muscles like those of grasshoppers. Instead, they control the blood pressure in their legs like a hydraulic system to propel them upwards.

By regulating the blood pressure within their legs, spiders, particularly jumping spiders, achieve remarkable feats like leaping multiple times their body length.

This hydraulic mechanism involves forcing blood to flow into the legs, causing a rapid extension and propelling the spider into the air with remarkable force, sometimes reaching distances up to 50 times their body length.

This jumping ability is not reckless; spiders often secure a silk dragline for safety in case of missed targets or precarious landings. Unlike insects with muscular legs, spiders lack extensor muscles in two of their six leg joints.

This absence of muscles makes them reliant on hydraulics for leg extension. This unique system, inherited from their ancestors, enables them to move efficiently and even walk on vertical surfaces using specialized bristles called scopulae. Interestingly, when a spider dies, its legs curl up due to the absence of blood pressure, which shows the crucial role hydraulics play in their movement and posture.

Spiders’ unique hydraulic system is a remnant from their pre-arthropod ancestors, with only a few extensor muscles located in the hip joints. Larger spiders use this hydraulic system in combination with flexor muscles for jumping, while smaller jumping spiders rely solely on hydraulics.