Notum

The notum is the dorsal portion of an insect's thoracic segment. Typically the notum is a single large sclerite, but often it is divided into the alinotum which bears the wings and the postnotum which bears the phragma. The phragma, or endotergite, is a transverse infolding of the intersegmental sclerite, and its main function is to provide a reinforcing basis of attachment for the dorsal longitudinal muscles. Accordingly phragmata tend to be best developed in actively flying insect species.