The posterior part of the mandible is called thorax. It is divided into three parts. Anterior thorax or prothorax, middle thorax or mesothorax and posterior thorax or metathorax. Each segment is covered by a cuticle made of chitin. It is called sclerite. The thoracic sclerite consists of three segments. Targum, pleuron and sternum. Dr. Siddiq Publications
(i) Targum: Dorsal sclerite of thorax is called targum. The thoracic targa are called notum. The targum of prothorax is called pronotum, the targum of mesothorax is called mesonotum and the targum of metathorax is called metanotum. Pronotum large, broad and elongated. The dorsal tergum consists of four sclerites. Prescutum, scutum, scutellum and postscutellum.
(ii) Pleuron: The lateral sclerite of thorax is called pleuron. Each lateral pleuron consists of three sclerites. Episternum, epimeron and parateron.
(iii) Sternum: The thoracic sclerite is called sternum. Sternum with a single sclerite. Dr. Siddique Publications