The movable jointed appendages around the mouth are called mouthparts. The mouthparts of grasshoppers are called mandibular mouthparts because they are used for chewing young leaves. It consists of five parts. Labrum, mandible, maxilla, labium and hypopharynx.
1. Labrum: The round, wide, bilaterally symmetrical and flattened organ attached to the clypeus on the surface of the head is called the labrum. It is also called the upper lip. It is sensitive. It covers the mandible and helps in grasping food items.
2. Mandible: On either side of the mouth there is a pair of strong, short and triangular mandibles or jaws. Each mandible has several dark grooves on the inside. These grooves are called molar processes or denticles. Each mandible has two types of muscles. These are-
(i) Adductor muscle: The muscle on the inner side of the mandible is called adductor muscle. It contracts and pulls the mandible inwards.
(ii) Abductor muscle: The muscle on the outer side of the mandible is called the abductor muscle. It contracts and pulls the mandible outward. The work of the mandible is to bite and crush the food.
3. Maxilla: On either side of the mouth opening there is a pair of multi-segmented maxillae along the mandible. It consists of two main parts. Cardo and Stypes. The base of the maxilla is called the cardo. The long and slender upper part of the cardo is called the stipe. Gallia and lacinia are present at the head of the stipe. Besides, there is a five-segmented maxillary pulp on the outer side of the stipes. Maxillary pulp is sensitive. The function of the maxilla is to pick food, catch food, feed food into the mouth and clean the front legs.
4. Labium: A multi-jointed large compound appendage located below the mouth opening is called labium. It means understanding the quality of food, putting the food in the mouth and covering the mouth. The labium consists of two main parts. Submentum and Mentum.
(i) Submentum: The base of labium is called sub mentum. It is flat and wide. It connects the labium to the skull.
(ii) Mentum: The part between sub mentum and pre-mentum is called mentum. It is small and almost round. There are two labial pulps on the outside. Each labial palp is composed of three lobes. At the tip of the mentum is a ligula. The ligula has glossa on the inside and par glossa on the outside.
5. Hypopharynx: The long, soft and fleshy appendage between labrum and labium is called hypopharynx or lingya. Its base is folded and covered with cuticle. The subtongue is involved in moving food and swallowing food.