''• ">">\ Vinal: Carolina Lo< 27 



superventral trachea l-II-h. (Plate III, Fig. i). The main spiracular 

 trachea also runs dorsally, giving off a hranch which gives rise to 

 the trachea; of each muscle layer. 



Ventral Thoracic Trachccc. — Thus far only the dorsal thoracic 

 trachea 1 have heen considered, hut all the important points connecting 

 two systems have heen noted. 



The main tube running antero-ventrally from spiracle /// (Plate 

 ///, Fig. 3, U ) and continuing forward through the thorax (Fig 

 to the head is the thoraco-cephalic trachea. This tube extends 

 each side of the ventral nerve cord to which it gives off many 

 branches. A superventral branch ( I-II-b.., Fig. t j arising from 

 spiracle / runs posteriorly, giving off a branch which forms an air 

 sac C (Fig. f), which in turn is almost directly connected with spi- 

 racle // | [V, Fig. 7, and Plate III, Fig. 3). Near this air 

 sac another branch is given off (Fig. I, g), which connects with the 

 ventral mesothoracic trachea given off by I-II-c of Fig. 3. Other 

 branches of this trachea run into the metathoracic muscles, where 

 they repeatedly divide, while the main tube ( II-Ik.) continues on and 

 enters the metathoracic leg. An anterior branch is given off near 

 air sac C, which supplies air to the salivary glands located in the 

 mesothorax. An air tube w (Fig. i), which arises from the lateral 

 spiracular trachea of the abdomen between spiracles /// and IV, runs 

 forward and joins with air sac / ; 1 Plate III, Fig. 3). 



(c) Abdominal Tracheal System. 



In comparison with the cephalic and thoracic tracheal system that 

 of the abdomen is simple. From each abdominal spiracle short air 

 tubes connect with a main longitudinal spiracular trachea (spt, Fig. 

 8, and Fig. 9), which extends from spiracle X forward on each side 

 of the abdomen to spiracle ///. From this spiracular trachea origi- 

 nate all the branches found in the abdomen. Typically in each seg- 

 ment of the abdomen bearing a spiracle, three main tubes are given 

 off by the spiracular trachea of that segment. One runs dorsally to 

 connect with an undulating longitudinal dorsal trachea and 

 leaving the spiracular trachea gives off a branch which bei 

 tended, forming a large air sac which is connected with the air 

 of both the preceding and following segments. A ventral branch is 

 also given off by the main spiracular trachea which unites with the 



