THE LOCUST OR SHORT-HORNED GRASSHOPPER 359 



TOPg 



cec- 



median portion, which is the brain proper, consists of three 

 parts that are indicative of its origin in the embryo from three 

 pairs of ganglia that have become 

 intimately associated. Posteriorly, 

 the brain is continued into the 

 circum-esophageal connectives which 

 extend on either side of the esophagus 

 to the sub-csophagcal ganglion. These 

 connectives give rise to the nerves 

 of the labrum, to a pair of nerves 

 that unite posterior to the esophagus, 

 and to a pair that unite on the 

 anterior face of the esophagus in the 

 frontal ganglion. From this ganglion 

 there arises a sympathetic system of 

 ganglia and connectives that inner- 

 vates the digestive system. 



The sub-csophagcal ganglion is a 

 compact globular mass without indi- 

 cations in the adult of its multiple 

 origin, but its three pairs of nerves 

 to the mandibles, the maxillse, and 

 the labium are indicative of its 

 origin from three pairs of ganglia 

 that have become intimately asso- 

 ciated. In the thorax are three pairs 

 of ganglia, corresponding to the three 

 pairs of appendages and joined by 

 connectives (Fig. 181 B). The 

 larger size of the third thoracic 



A, brain and circum-esophageal connectives 

 from posterior-dorsal aspect (cf. Fig. 17G), drawn 

 on a larger scale than the ventral nerve cord shown 

 in B. It, ventral nerve cord from dorsal view 

 a. 71., antennary nerve; al'. 1, ah. 3, and ab. 8, 

 abdominal segments; hr, brain; c.e.c, circum- 

 esophageal connective; e, esophagus; fg, frontal 

 ganglion; h, head; In, labral nerve; or, ocellar 

 nerves; op.g., optic ganglion; le, tentorium, an 

 internal portion of the skeleton; th. 1, th. 2, 

 and th. 3, thoracic segments. (.\fter Snodgrass, 

 loc. cit.) 



Fig. 181. — Xervou.s .system 

 of locust, Dissosleira Carolina. 



