The Development of the Wings of a Caddis-fly Platyphylax designatus Walk. 581 



to observe this is the regulär orientation of the wing rudiments in 

 both the mesothoracic and metathoracic segments. 



When the disk is well below the surrounding surface it does not 

 necessarily follow that it has taken 

 a certain definite shape. An exa- 

 mination of sections of a number of 

 wing rudiments in this early stage 

 shows that while in a large majority 

 the disk is quite regulär in appea- 

 rance, similar to figures 9A and 10^, 

 there are many exceptions. Text 

 figure II shows four of these irregu- 

 larities in which the disk is nearly 

 divided into two parts or the regular- 

 ity of the outer convex surface has 

 been lost. Such irregularities may 

 remain for some time during the 

 growth of the wing rudiment but do 

 not, we believe, in any way affect the 

 regularity of the wing of the imago. 



As already mentioned the peri- 

 podial pore at first decreases in 

 size and changes from a nearly circular to a more oval shape as the 

 disk enlarges; this is shown in figure 11 where the pore is not only 



— /P 



Text figure I. 



Surface view of a wing rudiment from the 

 metathorax, showing Position of its longitudi- 

 na) axis relative to that of the body of the 

 larva. D, dorsal; F, ventral; A, anterior; 

 P, posterior. The lower crescent-shaped space 

 between the lower, ventral, margin of the 

 wing rudiment and the adjacent wall of the 

 peripodial cavity. The more median hook- 

 shaped figure represeuts the dark chitin which 

 is always present. x 220. 



Text figure II. 



Four transverse sections from different larvae showing irregularities in the shape of the disk. 



x280. 



of an elongated shape but pointed at both ends, The elongation of 

 the pore was found in all specimens of about this stage but the pointed 



Zeitschrift f. wissensch. Zoologie. CV. Bd. 33 



