The Greenbug, Schizaphis graminum.1 4. Central and Stomatogastric Nervous Systems2

Abstract

The nervous system of the greenbug, Schizaphis graminum (Rondani) (Homoptera: Aphididae), is greatly condensed by the fusion of existing ganglia. The central nervous system consists of 3 main ganglionic masses; the cerebral ganglia, the suboesophageal ganglion, and the thoracic ganglionic mass. Detailed descriptions of different parts of the cerebral ganglia, the suboesophageal ganglion, the thoracic ganglionic mass, and the nerves arising from each of them are given. The nerves to the mouth parts and salivary glands were traced. Some embryological evidence is provided to show the origin and fusion of the suboesophageal, thoracic, and abdominal ganglia. The ventral nerve cord is a single longitudinal trunk extending to the 7th abdominal segment. It has 2 pairs of lateral branches in each segment, except the seventh where it divides and is transformed into many smaller branches. The stomatogastric nervous system consists of a frontal ganglion, a hypocerebral ganglion, 2 corpora cardiaca, and a single corpus allatum. All these endocrine glands are in close association with the oesophagus.