In the order Orthoptera, members chew their food, using their mandibles (jaws). Crickets are omnivores, which means they eat both plants and animals. Actually, they will eat almost anything: vegetables, cereal, and even their own mate if they are hungry enough. Katydids are mostly herbivores (plant eaters), though they will eat their own mate, too, if "they" are hungry enough. They also enjoy eating aphids and other small, slow-moving creatures. Grasshoppers almost always eat plants like grass, wheat bran, and lettuce, and they can be terrible crop pests.