BY R. J. TILLTAkt). 237 



drops upon the pseudo-cubitus, and dividing to send" two branches 

 to the wing-bordei'. Thus, instead of two isolated separate cells 

 being enclosed between Mj and Mn, as in the forewing, only one 

 elongated cell lies between them. In the imaginal venation, 

 this long cell is divided across the middle by a cross-vein. The 

 two portions may be called the frst and second intra-mediau 

 cells, with the notation im-^ and im„, as in the forewing. It will 

 be noticed that Mo in the hindwing forms about twice as large a 

 portion of the pseudo-cubitus as it does in the forewing. 



(3) The true Cubitus (Cu).— The course of this trachea, and of 

 the resulting veins in the imaginal wing, is so different in fore 

 and hindwings that these must be dealt with separately. In 

 the forewing, trachea Cu bends sharply up towards M, quite 

 close to the base. It then runs almost straight to the cubital 

 fork, cw/; which lies at a level half way between the base and 

 mf. From cuj\ Cuj runs almost straight on until it meets M„ 

 dropping on to the pseudo-cubitus; it then gives ofi" two descend- 

 ing branches, and finally drops to the wing-border. In the 

 venation, the basal approach towards M becomes a fusion, the 

 bend being excessive. Then follows a nearly straight portion, 

 which expands laterally so as to appear almost like two veins 

 running side by side for some distance from cw/" (shown in Plate 

 X., by a thickening of Cuj). I do not know the reason for this, 

 and have not been able to detect any thing but the single trachea 

 Cu, in this region of the pupal wing. The rest of the vein Cu, 

 forms a portion of the pseudo-cubitus, together witli the three 

 transverse veins descending to the wing-border. Cuo diverges 

 slightly from Cu,, and runs in a gentle curve to the wing-border, 

 ending up just before the most proximal branch of Cu,. In the 

 venation, two cross-veins connect it with Cu,, and a short, 

 strong cross- vein descends from it on to lA, just distad iromcuj'. 



In the hindwing, Cu is not fused basally with M. The main 

 stem of Cu is shortened, so that cu/ comes to lie very close to 

 the base, at a level proximad to that of m/! From cuf, Cu, runs 

 straight on until it gives off its most proximal branch, when it 

 performs the extraordinary evolution of arching up to meet M.^, 

 and so reaches the level of the pseudo-cubitus, of which it now 



