During the course of this research a detailed morphological study has been made of M. differentialis, the differential locust. The external sclerites and the internal ridges and apodemes have been described and shown in drawings. The muscular, digestive, respiratory, nervous, circulatory, and reproductive systems were described and diagrammed;Several kinds of glands have been located, drawn, and described. The corpora allata, a pair of endocrine glands, were described. The oenocytes, some attached to the ventral surface of the dorsal diaphragm and others attached to the small tracheae near the third, fourth, and fifth spiracles, been shown, Mono- and binucleate, oval and pointed nephrocytes, have been located in the pericardial sinus and the thoracic part of the ventral sinus;The minor as well as the major distinct muscles have been located and diagrammed. Their origins and insertions have been given. When one lists the muscles described and accounts for their duplicates in the other side of the body and in duplicate segments of the abdomen the total sum is obtained. There are ninety-four muscles in the head, and one hundred ninety-eight muscles in the neck and thorax. In the female abdomen there are two hundred seventy-six while in the male abdomen two hundred ninety-four occur. The female has a total of five hundred sixty-eight body muscles and the male a total of five hundred eighty-six. In addition to these distinguishable muscles there are the muscle sheets in the tubes and ducts of the various systems;The writer has tried to make this research comprehensive and yet has tried to make an intensive study of most of the systems.