Spiders are not insects. They are distinguished from insects by having eight, instead of six legs. They are characterized by a fused head and thorax (cephalothorax), eight eyes, a pair of sensory pedipalps, and 2–6 silk-producing spinnerets at the tip of the abdomen. Most spiders are venomous to their prey, but generally harmless to humans. Large spiders may bite defensively, inflicting minor pain. Most spiders are predators that hunt and feed on insects, and some feed on vegetation.