BY R. .1. TILLYARD. 069 



K-t+5 iu forewing, or Rs in hindwing, at metamorphosis; while 

 Ma likewise becomes hitched on to Cu, 



la" 



Moreover, the whole of trachea M becomes aborted at meta- 

 morphosis, so that M 2) is cut off from its original source of 

 supply. In the fresh imaginal wing, this trachea is seen to 

 have become hitched on to M 3 in the forewing, but on to Cu x 

 in hindwing. This must evidently be effected by the outgrowth 

 of a small trachea such as that which captured M3, though this 

 outgrowth did not begin to appear in the late pupa, and must 

 have developed during metamorphosis. 



The final result, in the forewing, is that no part of the true 

 main stem of M, either trachea or vein, is visible at all. In 

 the hindwing, however, a delicate groove indicates the position 

 <»L' M. together with its forking into two distally. This is shown 

 by a dotted line in Text-fig. 91, d. 



A further remarkable change at metamorphosis is the com- 

 plete abortion of the stem of R44.5, both trachea and vein, in 

 the forewing, as far as the inter-radial cross-vein ir, which is 

 present in Wingia, as also in Carpocapsa and all archaic Tor- 

 tricina and Tineina. The manner in which this is brought 

 about can be seen from Text-figs. 91, a, b. It has already been 

 mentioned that, during pupal life, a small trachea grows out 

 from R44.5 in the forewing towards Mj. This small trachea 

 traverses the cross-vein ' r-m, which appears quite early in pupal 

 life, with the rest of the imaginal venation. Above this cross- 

 vein, and in line with it, the cross-vein ir is also to be seen in 

 the pupal wing, and it is this cross-vein which furnishes the 

 channel for the greater change at metamorphosis. For, at that 

 time, a further trachea grows out from R 3 along ir, and cap- 

 tures both R 4+ 5 and its already attached M r ; while, at the 

 same time, the trachea R 4+5) basad from ir, shrivels up, — the 

 final result being as shown in Text-fig. 91, c. 



Turner (32, p. 172) has already pointed out, from a study 

 of the imaginal venation only in the Tortricina, that the large 

 basal cell is really a composite structure, formed from both the 

 true basal cell and the areole or radial cell; to this composite 

 cell he has given the name areocel; while the basal part of 

 R 4-1-5 ? which separates the true basal cell from the areole, and 

 by the elimination of which the areoci?l is 'formed, is called by 

 him the chorda. What he has failed to emphasise is the fact that 

 the cross-vein ir is present, and forms the boundary of the 



