318 The Ohio Journal of Science [Vol. X\"I, No. 7, 



Musculature System. 



The most noteworthy features of the musculature system 

 are the powerful muscles of the posterior region of the abdomen. 

 The pygofer bears the muscles which support and work the 

 strong ovipositor. The longitudinal muscles of the abdomen 

 comprise the small ventral muscles of the body wall and the 

 dorsal muscles. They are segmentally arranged. The lateral 

 muscles of the abdomen are poorly developed and are confined 

 to small strands which are situated along the sides of the body. 



Nervous System. 



The central nervous system (PI. XXII, Fig. 32) consists of 

 the brain (supraesophageal ganglion), the subesophageal gang- 

 lion, and the thoracic ganglion, with their attendant nerves 

 and commissures. 



The Brain (Br.) is relatively large and occupies the greater 

 part of the dorsal region of the head. It emits two pairs of 

 large nerves, which innervate the eyes (On.) and antennae (An.) 

 respectively. The brain is connected with the subesophageal 

 ganglion by the circumesophageal commissures, which are 

 rather small and not easily recognised. From the subesophageal 

 ganglion small nerves pass to the maxillae and labium. 



The Thoracic Ganglia (T. G.) are fused into one large 

 ganglion, located on the floor of the mesothorax. Small 

 commissures connect the thoracic ganglion with the sub- 

 esophageal, although the two appear to be continuous. Numer- 

 ous nerves originate from the thoracic ganglion and pass 

 to the legs, the dorsal muscles and the digestive apparatus. 



There are no abdominal ganglia, but two strong nerves 

 are seen passing back from the thoracic ganglion to the caudal 

 end of the body. These two main abdominal nerves (Abd. N.) 

 arise close to one another and are probably the result of the 

 separation of the abdominal ganglia and commissures. They 

 become widely separated as they pass down the body on either 

 side of the median line. Each abdominal segment is supplied 

 with nerves from these two main commissures and in addition 

 the reproductive organs, the digestive apparatus and the 

 excretory system are innervated. 



While the Jassid nervous system does not differ very much 

 from that of a generalized insect, it shows a specialization 

 in the absence of the abdominal ganglia. However, this is not 



