28 Journal New York Entomological Society. t Vo1 - xxvii. 



ventral tracheal system. In addition to the dorsal and ventral 

 branches a median tube is given off which supplies the alimentary 

 canal with its tracheae. 



In describing the abdominal tracheal system three main divisions 

 are recognized: (i) Dorsal, (2) ventral, and (3) alimentary tracheae. 



Dorsal Abdominal Trachea. — (Plate IV, Fig. 8.) In each seg- 

 ment of the abdomen bearing a spiracle, a dorsal branch, the dorso- 

 segmental trachea, is given off by the main spiracular trachea. These 

 branches connect dorsally with a right and left dorsal abdominal 

 trachea (da), which runs in close approximation to the alary muscles 

 of the heart. The dorsal abdominal trachea extends from spiracle 

 777 to beyond spiracle X, the latter spiracle being connected with 

 this tube by three dorsal segmental tracheae instead of one. The 

 right and left dorsal abdominal tracheae are independent and are in 

 no way connected by transverse tubes. 



The abdominal air sacs are closely associated with both the dorsal 

 and alimentary tracheal systems. There are eight of these sacs on 

 each side which originate as branches of the dorso-segmental tracheae 

 and those of each side are all connected by a longitudinal trachea 

 which runs along the top of the alimentary canal and reproductive 

 organs. These are usually found imbedded in the fat body. Over 

 the ileum in the sixth abdominal segment the right and left longi- 

 tudinal trachea connecting the air sacs unite to form the ileal plexus 

 (Ip). The air sacs arising from spiracles IX and X join directly 

 with this plexus as shown in Fig. 8. 



Ventral Abdominal Tracheae. — (Plate IV, Figs. 8 and 9.) In the 

 dorsal abdominal tracheal system the two dorsal abdominal tracheae 

 run contiguous to the alary muscles of the heart, but are in no way 

 connected with each other. In the ventral system a single ventral 

 segmental tube is given off by the spiracular trachea in every segment 

 bearing a spiracle. This segmental tube runs ventrally to join a 

 ventral abdominal trachea (va), situated on each side of the nerve 

 cord in every segment bearing a spiracle. Instead of the right and 

 left ventral abdominal trachea being separate they are joined by a 

 transverse tube which runs beneath the nervous system. This ven- 

 tral system gives off many branches to the nerve cord and at its pos- 

 terior extremity these tracheae give rise to branches which supply 



