BY R. J. TILLYARD. 



109 



Cuj a little distad from the fork indicates the position in the 

 imago of the posterior arculus, which is destined to form part of 

 the serial vein made up of the base of M, the posterior arculus, 

 and the distal portion of Cu]. A very careful examination of 

 the tracheae forming Ou in the pupal wing shows that the actual 

 dichotomy of Cu into its two main branches lies slightly basad 

 from the point which becomes the cubital fork in the imago, as 

 shown in Text-fig.2. It will be seen that the same type of 

 splitting back to a point before the actual bifurcation of the 

 imaginal veins is also to be found in all the other dichotomies, 

 not only in Eriocrania, but likewise in all Lepidoptera. 



Text-fig.2. 

 Portion of basal tracheation of forewing of the pupa of Eriocrania semi- 

 purpurella Steph., to show the cubital fork (Cu dividing into Cu x and 

 Cu.,), the posterior arculus (pa), the anal furrow (af), the ciibito-anal 

 cross- rein (cu-a), and the courses of the tlrree anal veins, with the sub- 

 anai cross-vein (•>«)• Note the splitting hack of the cubital ti'achea 

 basad from the true position of the cubital fork in the imago; also the 

 macrotrichia developed along the courses of the future first and second 

 anal veins; ( x 132). 



Careful dissections of the pupal forewings of Hepialidcp show 

 that this family also possesses the same conditions in the region 

 of Cu, the arching up of Cu, and the position of the posterior 

 arculus being exactly the same as in Eriocrania. The differences 

 between the two wing-types lie only in the more generalised 

 shape of the Hepialid wing, the more basal position of the 



