[duporte] LARVA OF SPHIDA OBLIQUA WALKER 241 



At a short distance from the origin of the intestinal nerve there is a 

 longitudinal slit in nerve E through which the vas deferens passes. 

 The presence of this slit is rather difficult to account for as no nerves 

 are sent to the vas at this point, nor is there any organic connection 

 between the vas and the nerve. The formation of the slit might 

 possibly be accounted for on the assumption that nerve E is the result 

 of the fusion of two nerves, one of which originally passed beneath 

 and the other above the vas. When two such nerves coalesced they 

 would naturally remain unfused at this point in order to allow the 

 passage of the vas deferens. This tends to confirm the assumption 

 that the terminal ganglion is the result of the fusion of at least three 

 ganglia. An embryological investigation would be necessary in order 

 to settle these points. 



Branch c is given off back of the slit and runs inwards innervating 

 the integument near the opening of the cjaculatory duct. Branch d 

 divides into several nervelets which innervate the integument near 

 the anus. Branch e innervates the muccles of the proleg, / goes to 

 the rectum and g innervates the last proleg. 



The Sympathetic Nervous System. 



The sympathetic nervous system of insects consists of, (1) The 

 median unpaired system, (2) the paired lateral system, and (3) the 

 ventral or superadded system. These systems are connected with the 

 central system, and usually the lateral and median systems are con- 

 nected. All three systems are present in the larva of Sphida obliqua 

 and will be described separately in the order given above. 



1. THE UNPAIRED MEDIAN SYMPATHETIC SYSTEM. 



This is also known as the Stomatogastric or vagus system. It 

 is connected with the central nervous system by means of the arched 

 nerves. 



The Arched Nerves, (figs. 3 and 7, Ar.), arise in connection 

 with the clypeo-labral nerves below the origin of the optic nerves. 

 They run forward for a short distance and after separating from the 

 clypeo-labral nerves, they curve inward and enter the frontal ganglion. 



The Frontal Ganglion, (figs. 3 and 7, fg.), is a small ganglion 

 situated on the medio-dorsal line of the pharynx, in front of the 

 supraoesophageal ganglion. 



The Frontal Nerve, (figs. 3 and 7, fn.), arises from the middle 

 of the anterior border of the frontal ganglion and projects forward 

 immediately above the pharynx. At a short distance in front of the 



Sec. IV, 1914—22 



