Most arachnids are predators, feeding on insects and other animals without backbones (invertebrates). Special mouthparts are adapted to catch, eat, and digest prey. On each side of an arachnid's head is a pedipalp, a jointed appendage that commonly looks like a mini leg. A pedipalp helps an arachnid to feel prey (It is also used for sperm transfer during mating by spiders). Because most arachnid eyes seem to be low-resolution light and dark sensors, an arachnid relies more on its sense of touch to feed. A pair of chelicerae on the front of an arachnid's body serve as jaws. Packed with muscles, they move from side to side or up and down to impale and chew prey. Hollow fangs at the tips of spider chelicerae are used to inject the prey with digestive juices or venom. Some arachnids also make silk to catch and immobilize prey.