Spiders foot. Coloured scanning electron micrograph (SEM) of a spiders foot, showing claws, and gripping and sensory hairs (setae). Taken from a spider exuvia (molt). The claws on a spiders feet are used to grip rough surfaces, while the setae are used to grip smooth surfaces. These setae enable the spider to cling to smooth surfaces by taking advantage of weak intermolecular forces, known as Van der Waals forces. The longer hairs are sensory structures. This is a foot of the jumping spider. Magnification: x500 when printed at 10 centimetres across.