THE LOCUST OR SHORT-HORNED GRASSHOPPER 355 



Respiratory, Circulatory, and Excretory Systems. — The external 

 openings of the respiratory system have been noted as the spiracles 

 that occur on the segments of thorax and abdomen. Leading 

 from the spiracles are the trachere or tracheal tubes. These con- 

 sist of a complex set of larger tubules from which arise innumer- 



FiG. 177. — Respiratory organs of 

 locust, Dissosteira Carolina. 



A, trachefp branching from spiracles of 

 third thoracic segment to digestive tract 

 as seen dorsally. B, anterior end of 

 abdomen showing spiracles and tympanic 

 membrane from lateral view. 06. 2, 

 second abdominal segment; g.c, gastric 

 caeca; sp, spiracle; th., first thoracic seg- 

 ment; ty, tympanic membrane. (After 

 Snodgrass, loc. citA 



>tr 



t.m 



Fig. 178.— Heart of locust. 



ao, aorta; br, brain; d, mem- 

 brane ventral to heart, some- 

 times called the diaphragm; 

 h, heart; t.m., thoracic muscles; 

 tr, tracheiE. (After Snodgrass, 

 loc. cit.) 



able lesser ones (Fig. 177). In the abdomen there are sac-like 

 enlargements of the tracheae, the air sacs, that serve as reservoirs. 

 The lesser tracheae branch and re-branch until they end blindly as 

 microscopic subdivisions in all parts of the body. So extensive is 

 this branching that no bit of tissue is far removed from one of these 

 tracheal tubules. 



