[duporte] LARVA OF SPHIDA OBLIQUA WALKER 239 



Nerves of the Third, Fourth, Fifth and Sixth Abdominal 

 Ganglia. (Fig. 1, III, IV, V, and VI.). Nerve A is practically identi- 

 cal with the corresponding nerve of the second ganglion. 



Nerve B. The proximal branch a runs forward, and near its 

 origin gives off two nerves, one of which enters the leg and the other 

 goes to muscles near the opening into the leg. After giving off these 

 nerves branch a forks and the two branches go to the integument near 

 the anterior suture. From one of these nerves a minute branch runs 

 to one of the setae, near the median line, and from the other a very 

 small nerve runs in a lateral direction, terminating beneath the 

 tracheal trunk. The description of nerve B of the first and second 

 abdominal ganglia will also serve for this nerve except for the first 

 branch just described. 



Nerves of the Last Abdominal Ganglion. (Figs. 1 and 5, 

 VII.). This is the largest of the abdominal ganglia and is usually 

 situated on the line between the sixth and seventh abdominal seg- 

 ments, though it may be wholly within either one of these segments. 



This ganglion is made up of at least two pairs of primitive gang- 

 lia, those belonging to the seventh and eighth abdominal segments. 

 It is probable however that there are three ganglia concerned in the 

 fusion. There is no indication of this in the ganglion itself but the 

 fact that there are five pairs of nerves given off upholds this view. 

 The nerves of this ganglion may be homologized with those of the 

 other abdominal ganglia. The homology between nerve A of this and 

 the other ganglia is readily seen from the distribution of the branches. 

 Nerve B, too, corresponds to nerve B of the other abdominal ganglia. 

 Nerves C and D the writer regards as belonging to what was originally 

 the eighth ganglion. These two nerves almost invariably arise to- 

 gether and coalesce for some distance, and this may be regarded as an 

 indication of their origin from the same ganglion. It is more difficult 

 to homologize these nerves with those of the other abdominal ganglia, 

 but the fact that the lateral nerve of the sympathetic system is in 

 close connection with C, and that D goes exclusively to the venter are 

 indications of the homology of these nerves with A and B respectively 

 of the other ganglia. Nerve E may have formerly belonged to a ninth 

 ganglion. The presence of only one pair of nerves may be due to the 

 elimination of the second pair or to the fusion of the two pairs. 



Nerve A. The anterior nerve of the terminal ganglion arises at 

 the lateral border of the ganglion and runs back obliquely passing 

 above the ventral recti minores and beneath the recti majores. It 

 crosses into the back mesad of the tracheal trunk and runs above 

 the dorsal recti muscles. The first branch a is given off beneath the 

 ventral recti muscles and innervates some of these muscles. Nerve 



