ANATOMY OF THE GOUT-FLY OF BARLEY. 



793 



three slioit arms of the felted chamber. In neither anterior nor 

 posterior stigmata have I been able to distinguish any Stigmatic 

 Scar, According to ])e Moijere, tho visibility of this structure 

 varies greatly in dilFerent s[)ecies. It is, however, probably 

 present in all third instar Cyclorrhaphous larvte. 



On each side of tlie body there is a dorso-lateral main tracheal 

 trunk uniting the anterior and postei'ior stigmata of its side 

 (text-fig. 9, l.t.). Uniting the two dorsal trunks are a series of 

 ten dorsal commissures, the second of which is rather strongly 

 looped forwards, the remainder being practicn.llj'- transverse. The 

 iirst and tenth commissures, particularly the latter, are thicker 

 than tlie intervening ones; the first gives off f I'om each end an 

 anteriorly dii-e(;fced branch which goes to the pharyngeal mass ; 



Text-figure 7. 



Dorsiil view of po'sterior spiracle. (The stigmatic plate is seen b}' 

 transparence.) 



the reiBainder are quite devoid of branches. The middle point 

 of each commissure shows a small rounded thickening which 

 sections show to be attached to the dorsal body-wall by a slender 

 suspensory ligament. The distribution of the dorsal commissures 

 is as follows : — No. 1, anterior region of body-segment 3. No. 2 

 middle of segment 3, but looping strongly forwards. No, 3, 

 anterior region of segment 4 (i. e. Hrst abdominal). No. 4 arises 

 at about the junction of segments 4 and 5, and nos. 5-10 arise 

 similarly at the points of junction of the other body-segments. 

 There is no transverse commissure at the point of junction of 

 segments 11 and 12. 



Each dorso-lateral trunk gives off eleven lateral trunks, the 

 anterior three of Avhich are small and are mainly disti'ibuted to 



