Pronotum, the saddle-shaped shield on the prothorax used for protection, covers the 1st segment of the thorax where the first pair of legs are attatched.
The thorax, locomotion center of the grass-hopper, is a stout, boxlike structure consisting of three fused segments: the prothorax, mesothorax, and metathorax.
Each segment bears a pair of legs. The second segment bears a pair of fore-wings, the tegmina, and the third segment a pair of membranous hindwings. The wings of a few species are reduced to small pads or are entirely lacking. The top of the thoracic segments is called the notum, the bottom the sternum, and the sides the pleura.
The pronotum situated just behind the head is a prominent, saddle-shaped structure with lateral lobes that hide nearly all of the propleura.
The pronotum has many distinctive features useful in separating both genera and species of grasshoppers.
The integument (skin) may be nearly smooth in some species and rough and wrinkled in others. The dorsum or disk of the pronotum is divided into left and right halves by a longitudinal ridge, the median carina.
The ridge varies among species from barely visible to a conspicuously high crest. Transverse furrows run across the disk and down the lateral lobes. These furrows, known as sulci, cut into the median carina and divide the disk into zones, the prozona in front and the metazona in the rear.
In many species only one sulcus cuts the median carina while in others two or three sulci cut the median carina. The hind sulcus is considered the principal sulcus; from its position the length of the prozona and metazona are measured.
For more info, see UWYO.edu's Detailed Grasshopper External Anatomy.