No. 4-] METAMORPHOSIS OF THE FLAG WEEVIL. iS'' 



o 



leg. A wing bud would differ only in having the inner surface 

 of the hypodermis free from tracheae, etc. 



The striking difference between the behavior of the cells in 

 these buds, and the behavior of hypodermis cells elsewhere 

 (observed, doubtless, by every one who studies sections of insect 

 larvae), I have thought it worth while to emphasize in this figure. 

 Fig-. 2, A, shows the crumpling which precedes molting every- 

 where except in these buds. Fig. 2, B, is a bud, and shows 

 instead the thickening of the hypodermis and the compression 

 of its cells. Elsewhere the hypodermis stretches as it grows ; 



'B 



FIG. 2. Two dispositions of hypodermis. ^.vertical section of the frons at the end of the second 

 larval stage, showing the crumpling of the hypodermis. B, vertical section of the bud of 

 the middle leg at the time of molting at the end of the second larval stage, showing the 

 thickening of the hypodermis, without crumpling, c, old chitine ; c ', new chitine ; in, 

 developing muscle fiber; t, trachea. 



the cells separate as they multiply ; and that is true also of the 

 hypodermis of the appendages, later, when the time has come 

 for their extension. This we call retarded development, but the 

 physiological explanation of it is still lacking. 



There is no imagination of wing and leg buds in this beetle. 

 Even the shallow hypodermal pockets formed about them in 

 the more generalized Coleoptera are absent. The buds do not 

 retreat from the surface. Fig. i shows their appearance as 

 seen through the thin integument of the full-grown larva. 

 Fig. 3 is a section of the wing at this time. The inner wall 

 of the projecting shelf of hypodermis below the wing tip is all 

 there is to represent the so-called "peripodal membrane." With 



