'29'2 Secretion of iiotassuiiit hydroxide hy 1). vinula. 



"shield." The only one I saw free itself did so at the 

 moment it met a vertical surface when crawling along a 

 horizontal board ; it looked as though the animal struck 

 the shield accidentally against the vertical side of the 

 box, and made an upward movement of the head prior 

 to ascending in order to let the wings hang down. But 

 from this single instance I cannot draw a general 

 conclusion. In this case the shield was on till the 

 vertical side was encountered, and then fell off at once. 

 Certainly, if the "shield " were pressed against a surface, 

 and the head drawn upwards, the former would easily 

 be removed by withdrawal of the hooks from their sockets. 



Summarii. 



I. — The imago of D. vi)iula produces a solution of 

 potassium hydroxide, probably from the mouth, 

 in order to soften the cocoon, 

 II. — The labrum of the imago bears two sharply pointed 

 processes, used for scraping the inner surface of 

 the cocoon in order to break a way through. 

 III. — The eyes and median portion of the head of the 

 pupa are retained as a protecting shield over 

 the same structures of the imago until emergence 

 is completed. 



