Mantises are notable for their hunting abilities. They are exclusively predatory, and their diet usually consists of living insects, including flies and aphids; larger species have been known to prey on small lizards, frogs, birds, snakes, and even rodents. Most mantises are ambush predators, waiting for prey to stray too near. The mantis then lashes out at remarkable speed. Some ground and bark species, however, pursue their prey rather quickly. Prey are caught and held securely with grasping, spiked forelegs ('raptorial legs'); the first thoracic segment, the prothorax, is commonly elongated and flexibly articulated, allowing for greater range of movement of the front limbs while the remainder of the body remains more or less immobile. The articulation of the head is also remarkably flexible, permitting nearly 300 degrees of movement in some species, allowing for a great range of vision (their compound eyes have a large binocular field of vision) without having to move the remainder of the body. As their hunting relies heavily on vision, they are primarily diurnal, but many species will fly at night, and can be commonly encountered at lights.