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TEXT-BOOK OF ENTOMOLOGY 



represents a wing of a larva three days before pupation, with, the 

 germ of a thoracic leg. 



A. G. Mayer has examined the late development of the wings in 

 Pieris rapie. Fig. 149 represents a frontal section through the left 



FIG. 148. Graber' s diagrams for explaining the origin and primary in vacillation of the hypo- 

 dermis to form the germs of the leg (/>), and wings (/, A-C), and afterwards their evaginatioh D, 

 so that they lie on the outside of the body. E, stage B, showing the hypodernial cavities (/) and 

 stalks connecting the germs with the hypodermis (s). After Graber. 



wing of a mature larva and shows the rudiment of the wing, lying 

 in its hypodermal pocket or peripodal cavity. How the trachea 



passes into the rudimen- 

 tary wing, and eventually 

 becomes divided into the 

 branches, around which the 

 main veins afterwards form, 

 is seen in Figs. 144, 147, ir> ( .). 

 The histological condi- 

 tion of the wing at this 

 time is represented by Fig. 



1-n;. 1 111. >iTtion lengthwise through the left wing L J 



of mature larva In l'i,-rix fti/nr: t, trachea; hyp, hypo- 151, the Spindle-like hypo- 



(Ic-nnis ; c, cutirula. After Mayer. 



dermal cells forming the 

 two walls being separated by the ground-membrane of Semper. 



" While in the pupa, state," says Mayer, " the wing-membrane is 

 thrown into a very regular series of closely compressed folds, a single 

 scale being inserted upon the crest of each fold. When the butter- 



