154 GRAMMAR OF ENTOMOLOGY. 



on the segment in which they happen to be 

 situated, as the right spiracle of the prothorax 

 (prothoracis spiraculum dextrum) : the fact of a 

 segment possessing or not possessing spiracles is 

 of importance in classification. 



583. From each spiracle a single trachea enters 

 the body ; this single trachea is invariable ; but 

 the system of tracheae within, are on various 

 plans; the principal are the detached tracheae, 

 and connected tracheae. 



584. The tracheae are called detached when, 

 after entering the body as a single cylindrical 

 tube, they separate, diverge, and ramify, through- 

 out the region in their immediate vicinity, with- 

 out any obvious connexion with the trachea; of 

 the adjoining spiracles. 



585. The tracheas are called connected when 

 there is a grand longitudinal trachea traversing 

 each side of the body throughout its length, into 

 which each spiracle sends its particular trachese, 

 sometimes as a single tube, sometimes after a 

 slight ramification. 



586. Whether the tracheae possess the detached 

 or connected form, their minute branches may be 

 traced wandering over to the opposite side of the 

 insect, and uniting with similar minute branches 

 emanating from that side, so that the system of 

 respiration is always connected, and acts by uni- 

 formity of impulse. 



587. The ramifications of the tracheae to our 



