THE GEXERAL FEATURES OF WINGS 



73 



in an iiTegular manner by interpolation, i. e. by the splitting of various 

 members of a series of accessory veins. 



Illustrations of the adding of accessory veins distally are to be seen in 

 Corydalus and allied genera. The presence of fine twigs at the tip of 



Fig. 59. — Fore wing of a nym])h of a cockroach (After C. & X.). 



trachea R2 in the pupal wing of Corydalus (Fig. 58) indicates the method of 

 increase, which is doubtless as follows: the branches have been added one 

 after another to the tip of trachea R-j, there being a migration of the base 

 of each accessory trachea towards the base of the wing, thus making room 

 for the addition of new branches. In this case the first accessory vein is 

 the proximal one. 



In the wing of a nyinph of a cockroach represented by Figure 59 there 

 are manv accessorv trachea? branching from the front side of the radial 



fsi A 



Fig. 60.- — -A wing of a pui)a of Chanliodes (After C. & N.). 



trachea. From the presence of the iinc twigs near the apex of the wing, it 

 is evident that accessory tracheae are being added distally. It is also 

 evident that the number of accessory tracheae is being increased by the 

 splitting of some of these accessory tracheae, i. e., by interpolation. 



