12 Journal New York Entomological Society. [Voi. viii. 



circumference of it should be much increased. Now this is not the 

 case. The second and third segments are swollen only while they 

 contain the germs of the wings. After these organs issue the diam- 

 eter does not exceed that of the neighboring segments." Gonin ex- 

 plains the transition of the wings according to the theory of the 

 destruction of the envelope. As evidence of this he cites the fact 

 of there being a large amount of debris around the wing and between 

 the two layers of the integument. He also refers to the fact of hav- 

 ing a series of slides in which the front wing is entirely exterior while 

 the hind wing has not completed the transformation. 



I have observed all this, but I believe that this structureless sub- 

 stance referred to by flonin is none other than the moulting fluid. The 

 reagents act upon this substance, coagulating it, which gives it the 

 appearance of degenerating tissue. Stains act upon this substance 

 very vigorously, even more so than upon the hypodermis. But since 

 I find this structure around the entire larva (Fig. 29, ;///) as well as 

 around the wing, in about equal (quantities, I believe it has no con- 

 nection with broken down tissue. 



A careful study of Figures 18, 19, and 20 which were taken from 

 the peach-tree borer, Figure 18, from a caterpillar just before spin- 

 ning its cocoon. Figure 19, from one which had begun to spin its 

 cocoon, and Figure 20, from one which had just completed its 

 cocoon, will show the method of the transition of the wing from 

 the inside of the body cavity to the outside. It is found that the 

 dorsal part of the wing (c/ ) emerges first. Figure 18, .v shows the 

 two layers of the hypodermis, the one the external hypodermis and 

 the other the peripodal membrane, drawn back a little but not fused 

 as shown in Figure 19, .v. The fusion of the two layers and the draw- 

 ing dorsad in the direction of the arrow in the latter case is very evi- 

 dent. In the stage shown in Figure 20 the dorsal fold at .v has 

 entirely straightened out. During this time the wing has grown con- 

 siderably as shown by the relative size of the figures. Figures 19 and 

 20 both being drawn to the same scale. The same result is shown by 

 the ventral fold v. In the stage represented by the first two figures 

 the walls have not fused, while it is easily seen that they are coming 

 closer together in the course of the development. In the third case, 

 represented in Figure 20, the walls have fused at v and drawn ven- 

 trally in the direction of the outside arrow. During the course of the 

 development the wings now grow very rapidly in the direction of the 



