If you’ve ever watched a spider run, jump, or even swim, you might have wondered how it does it. These creatures aren’t much different from other arthropods, but they’ve got some extra special features that make them unique.
They’ve got an unusual jointed exoskeleton that houses a large network of fluid. These liquids help them generate pressure and power to propel their bodies. They also facilitate predation. Some spiders have fluid-powered genital movements, which can enhance copulation. This may even increase the number of sperm transfers.
Spiders also have an extensive hydraulic network that provides a strong force to the hind legs. These forces are generated from pressurized liquids stored in the cephalothorax, the middle dome of the spider’s body. They’re primarily responsible for the propulsion of spiders.
However, large spiders do not use hydraulics for their propulsion. They instead depend on the combination of hydraulic catapult and muscle-based contractions. The hind legs are used to launch the centre of mass off the substrate.
The smaller spiders rely mainly on hydraulic catapult. They are usually under 3 grams in weight. This means that their leg pairs need to shorten during the process of propulsion.
Larger spiders can still benefit from the use of hydraulic torques. Despite this, they do not have a distinct jumping sequence. As a result, they are vulnerable to damage or deflation. They can also bounce, but must use excessive muscle energy to maintain a constant bounce.