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.