268 REPORT UNITED STATES ENTOMOLOGICAL COMMISSION. 



riG. 17. 



Fig. 16. 



Fig. 16.— Showing distribution op air-tubes (trachea) and air-sacs.— Side view of the body. 

 V, main ventral trachea (only one of the two shown) ; s, left stigmatal trachea, connecting by vertical 

 branches with D, the left main dorsal trachea ; c, left cephalic trachea ; oc, ocular dilated trachea. 

 • Fro.m the first, second, third, and fourth spiracles arise the first four abdominal air-sacs, which are suc- 

 ceeded by the plexus of three pairs of dilated tracheae, 1, 11, III, in Fig. 17. ISTumerous air-sacs and 

 tracheaj are represented in the head and thorax. The two thoracic spiracles are represented, but not 

 lettered. 



Fig. 17.— D, left dorsal tracnea; S, left stigmatal trachea; I, II, III, first, second, and third pairs 

 of abdominal dilated tracheae, forming a plexus behind the ovaries ; 1, pair of enormous thoracic air- 

 sacs ; 2, pair of smaller air-sacs; 3-7, abdominal air-sacs ; oc, ocular dilated trachea and air-sacs ; c, 

 cophalic trachea. The relations of the heart to the dorsal trachesB are indicated. (Drawn by Emerton 

 from disaections by Packard.) 



