126 



AN INTRODUCTION TO ENTOMOLOGY 



system, and the peripheral sensory nervous system. The first of 

 these is connected with the brain ; the other two, with the thoracic 

 and abdominal ganglia of the central nervous system. 



The oesophageal sympathetic nervous system is intimately 

 associated with the oesophagus and, as just stated, is connected with 

 the brain. It is described by different writers under various names; 

 among these are visceral, vagus, and stomato gastric. It consists of two, 

 more or less distinct, divisions, an unpaired median division and a 

 paired lateral division. 



The unpaired division of the oesophageal sympathetic nervous 

 system is composed of the following parts, which are represented in 



Figures 141, 142, 143, and 

 144: the frontal ganglion 

 (fg), this is a minute gang- 

 lion situated above the 

 oesophagus a short distance 

 in front of the brain; the 

 unpaired nerve connecting 

 the frontal ganglion with the 

 brain (i), this is a small 

 nerve extending from the 

 brain to the frontal ganglion ; 

 the paired nerves connecting 

 the frontal ganglion with the 

 brain (ar) , these are arching 

 nerves, one on each side, 

 extending from the upper 

 ends of the crura cerebri to 

 the frontal ganglion; the 

 frontal nerve (fn) , this nerve 

 arises from the anterior bor- 

 der of the frontal ganglion 

 and extends cephalad into 

 the clypeus, where it bifur- 

 cates; the pharyngeal 

 nerves (pn), these extend, 

 one on each side, from the 

 frontal ganglion to the 

 lower portions of the pharynx ; the recurrent nerve (r} , this is a single 

 median nerve, which arises from the caudal border of the frontal 

 ganglion, and extends back, passing under the brain and between the 



oes 



Fig. 143. Dorsal view of the nerves of the 

 head in the larva of Corydalns; e, ocelli; 

 mnd. mandible; other lettering as in 

 Figure 142 (From Hammar). 



