THE NERVOUS SYSTEM
The nervous system consists of the brain, the subesophageal ganglion, and the ventral nerve cord, together with branches of these structures. The brain is a large mass of nerve tissue in the head just above the esophagus. The two optic nerves which supply the large compound eyes make up the principal part of the brain, being much larger and more complicated than the cerebrum, which is supposed to be the organ of sensation.
The subesophageal ganglion is a sort of second brain lying just below the esophagus; it gives off nerves which supply the mouth parts and control the mechanism of feeding. The ventral nerve cord runs back from the subesophageal ganglion and traverses almost the entire length of the body, being analogous to the spinal cord of the vertebrates. It bears three ganglia in the thoracic region which give off nerves to the legs, wings, and thoracic muscles. Other ganglia, located in the abdomen, have many branching nerves which are distributed to the abdominal muscles and the viscera.