292 DESTRUCTIVE INSECTS. 



Their injury to these forest-trees is, however, imper- 

 ceptible. 



But the most destructive coccus in this country is 

 what is called the American blight, or mealy aphis. 

 This is the great pest of our apple orchards, and to 

 the same kind of trees in nurseries. The young are 

 so exceedingly minute, that they can, apparently, 

 enter the pores of the epidermis, cause a swelling of 

 the cuticle, w^ich soon after bursts. The insects 

 then may be seen in the openings, covered with a 

 white efflorescence ejected from their bodies, intended 

 it would seem, either for the purpose of concealment, 

 or as a protection, instead of the scales with which 

 their less destructive congeners are provided. 



As this species seems to prey on the juices which 

 flow between the bark and wood, or on the tender 

 substance of the envelope itself, the former year's 

 wood becomes denuded, and the lacerated edges of 

 the wound become corky and monstrous, increasing 

 in size till it encircles the branch, when all communi- 

 cation with the roots is cut off; of course the branch, 

 or if the insects have seized the stem, the whole head, 

 dies. Their manner of living and breeding is similar 

 to that of the others mentioned above ; the females at- 

 tain the size of linseed nearly, and are constantly enve- 

 loped in the white covering peculiar to them, and by 

 the buoyancy of which, it is said, they are wafted from 

 tree to tree. They fix on the roots as well as on the 

 branches of trees, and thus out of sight are often 

 extensively injurious. The male is said to be a small 

 black fly. The blood of these insects, if such it may 



