114 Annals Entomological Society of America [Vol.1, 



anterior region of its segment. From above, the ganglia and 

 the proximal portions of their nerves are protected by the ventral 

 diaphragm, the outline of which is indicated in Figs, i, d, d, by 

 dotted lines. 



The connectives of the abdominal ganglia consist of two dis- 

 tinct cords connecting the successive ganglia. Those of the first 

 and last ganglia are very short because of the ccphalization in 

 these regions. The cephalic ends of the connectives are generally 

 closely approximated, while the middle and caudal portions are 

 slightly spread apart, so that the minute median nerve of the 

 sympathetic system becomes exposed between the two connec- 

 tives. In the abdomen there are no nerves arising from the 

 connectives, such as were found in the thorax. 



The Nerves of the Abdominal Ganglia. 



The nerves arising from the first seven ganglia are pretty 

 nearly uniform both in number and distribution. Fig. 3, repre- 

 senting the right side of the third segment, illustrates the typical 

 condition of the nerves of the abdominal region. From each gan- 

 glion two sets of nerves arise, one pair lateral and one pair 

 ventral. 



The lateral nerve (/) extends laterad over the ventral 

 muscles. It gives rise to five branches, which generally extend 

 caudo-laterad to the different parts of the corresponding segment. 

 Branch i originates from the cephalic side, near the base of the 

 main trunk. It is a very small nerve and can be detected only 

 in well prepared specimens. The distal end of this branch unites 

 with the transverse nerve {tv. n.) forming a single nerve, which 

 extends laterad to the minute tracheal nerve* {tr. n.) Branch 2 

 consists of a large nerve originating from the caudal side, a few 

 mihimeters from the base of the main trunk. It extends caudo- 

 laterad over the neighboring muscles (Fig. i, m^) and then turns 

 ventrad and innervates the deep lying ventral muscles. Branch 

 7 arises shortly distad of branch 2. It is a rather large nerve, 

 passing latero-caudad over the ventral muscles. On reaching 

 the outer border of these muscles, the nerve passes underneath 

 a few muscle-fibers (Fig. i, m. and Fig. 8, v^ m^ of the same 



* Since the nerves of the tracheal system have not been considered in this 

 paper, in may be necessary to state that such nerves have been observed lying 

 closely connected with the trachea and in certain instances dividing in such a 

 way as to supply each tracheal branch. The tracheal nerves are connected 

 with both the central and the sympathetic systems. 



