The labrum, located to the front of the upper jaw, is inflexible and hard. Like the rest of the grasshopper exoskeleton, it is made of chitin, a chemical compound derivative of glucose. Located above the lower jaw, or labium, and below the clypeous, which is a small part of the head, the labrum is one of the many pieces that form the mouth of a grasshopper. The labrum is flat and round-shaped.
Chemoreceptors are structures linked to the sensory nerves, present in the mouth, legs and antennae of grasshoppers. Gustatory and contact chemoreceptors are found in the labrum, as well as in other mouth-parts, such as the clypeous. These chemoreceptors are more numerous in adults than in nymphs, which are young and sexually immature grasshoppers.
Grasshoppers prefer to eat grasses, many of which are cereal crops, but can feed on most plants when grasses are not available. Some species of grasshoppers choose a few host plants to feed on, while others can eat almost any leaf. The creosote bush grasshopper (Bootettix argentatus) is the only species that feeds on one plant species only, the creosote bush.
In addition to the labrum, clypeous and labium, grasshoppers have other pieces that form their mouths. They have a pair of rigid mandibles, which play an important role in the chewing of food before ingestion. Palps are segmented appendages that extend from the labium and the two maxillae, which are found behind the mandibles. Grasshoppers also have salivary glands, which helps to digest food when still in their mouths.