The Scale Insects 



the tree which seem to be seriously affected. Older twigs, how- 

 ever are also attacked, and many specimens of the insect may be 

 found upon the trunk. As soon as the young insect finds a 

 suitable position it gradually inserts its beak and commences to 

 grow through the influence of the healthy food sap which it pumps 

 up. Almost immediately, also, the secretion of scale begins. 

 This is first noticed in the form of a white, waxy powder which 

 first is seen in the form of threads, but which soon becomes homo- 

 geneous. In a few days the first molt takes place, not as in the 

 ordinary manner with insects by a series of contractions and exten- 

 sions which work the old skin to the end of the body, from which 

 it is finally freed, but by a sort of loosening and shrinking of the 

 body underneath, all the parts except the proboscis being shed 

 and abandoned with the skin. Strengthened by the secretions 

 from the body, this skin forms the first scale. Presently the skin 

 is shed a second time and mingles with the second secretion, 

 which forms the second scale, which may be noticed at the 

 anterior end of the completed scale of the old individual. As 

 growth continues this second scale becomes too small and is 



Fig. 152. — The scurfy bark-louse of the 



apple, Chionaspis furfurus. 



(Author's illustration.) 



lifted up into the third portion, while the shield proper is secreted 

 by a series of increments, more being constantly added on behind 

 as the insect beneath grows. When full grown the female is 

 ready for reproduction. The male scale is a perfectly distinct 



257 



