152 



Beekeeping 



dioxid enter the tracheal branches and are expelled through 

 the spiracles. The more complex compounds are eliminated 

 in the process of excretion. 



The tracheal system of the bee is shown sufficiently in 



the accompanying il- 

 lustration (Fig. 79) so 

 that a detailed de- 

 scription is uimeces- 

 sary. The abdomen 

 contains the unusu- 

 ally large tracheal 

 sacs (TraSc) connected 

 with each other by 

 ventral commissures 

 (TraCom). They are 

 also 'connected with 

 tracheal sacs of the 

 thorax. From the 

 most anterior spiracles 

 of the thorax are 

 heavy trunks to the 

 air sacs of the head, 

 above the brain. The 

 tracheal system of the 

 bee is more elaborate 

 than that of most 

 other insects and prob- 

 ably in no other 

 species is there more 

 free access of oxygen 

 to all parts of the 

 body. 



The pumping of the 

 air through the body is accomplished by the respiratory 

 movements of the abdomen, consisting of a lengthening 

 and shortening of the abdomen and a shght dorso-ventral 

 movement. The muscles of the abdomen which function 



Fig. 79. — Tracheal system of worker with 

 dorsal sacs and trunks removed, from above. 



