702 



Mr. T. H. Tavlor 



branch in the mctatliorax 

 may be similarly named. 

 The position of the an- 

 terior thoracic spiracle is 

 somewhat diflficult to 

 determine, but can be 

 inferred from the follow- 

 ing considerations. In 

 old larvae the developing 

 pupal gill obscures the 

 junction between the pro- 

 and mesothorax. In larvae 

 in which the rudiment 

 of the gill is beginning 

 to develop a vertical 

 muscle marking the in- 

 tersegmental junction can 

 be readily made out (fig. 

 2, vm). The spiracle is 

 situated posterior to the 

 muscle, and is therefore 

 mesothoracic in position. 

 Of the two branches 

 which are given ofif from 

 the spiracle - chamber 

 one is anterior and the 

 other posterior. Each 

 agaiu forks into a dorsal 

 and a ventral branch. 

 The dorsal member of 

 the posterior branch 

 unites with the succeed- 

 ing metathoracic seg- 

 mental branch (fig. l.c). 

 Each member of the 

 anterior branch again 

 divides, so that there are 

 four tracheae passing for- 

 wards, which may be 

 numbered from above 

 downwards the 1st, 2nd, 

 3rd and 4tli. The 4th 

 supples the })rothorax 

 and its foot, the other 



