THE EMBRYOLOGY OF THE HONEY BEE 169 



y 



TraCom 



FIG. 64. Side view of anterior end of larva about two and one-half days 

 old, treated with caustic potash, showing the tracheae and the endoskelleton 

 of the head. 



...Tae 



TraTr 



FIG. 65. Section through a spiracle (Sp), spiracular branch (SpBr) 

 and tracheal trunk (TraTr), of a newly hatched larva (Stage XV), 

 x 600. 



The spiracles are twenty in number, ten on each side, ranged 

 in a row along the lateral surface of the trunk, and correspond to 

 the second to the eleventh trunk segments, inclusive. All of the 

 spiracles are situated in the anterior half of the segment to 

 which they belong, the first three pairs lying close to the an- 

 terior margin of the corresponding segments. The form and 

 structure of a spiracle, together with the branch connecting it 



