212 INSECTS INJURIOUS TO VEGETATION. 



and fine down, and appear in the spring of the year like little 

 specks of mould on the trees. As the season advances, and 

 the insect increases in size, its downy coat becomes more dis- 

 tinct, and grows in length daily. This down is very easily 

 removed, adheres to the fingers when it is touched, and seems 

 to issue from all the pores of the skin of the abdomen. When 

 fully grown, the insects of the first brood are one tenth of an 

 inch in length, and, when the down is rubbed off, the head, 

 antennae, sucker, and shins are found to be of a blackish color, 

 and the abdomen honey-yellow. The young are produced 

 alive during the summer, are buried in masses of the down, 

 and derive their nourishment from the sap of the bark and of 

 the alburnum or young wood immediately under the bark. 

 The adult insects never acquire wings, at least such is the 

 testimony both of Hausmann and Knapp, and are destitute of 

 honey-tubes, but from time to time emit drops of a sticky fluid 

 from the extremity of the body. These insects, though desti- 

 tute of wings, are conveyed from tree to tree by means of 

 their long down, which is so plentiful and so light, as easily to 

 be wafted by the winds of autumn, and thus the evil will 

 gradually spread throughout an extensive orchard. The nu- 

 merous punctures of these lice produce on the tender shoots a 

 cellular appearance, and wherever a colony of them is estab- 

 lished, warts or excrescences arise on the bark ; the limbs thus 

 attacked become sickly, the leaves turn yellow and drop off; 

 and, as the infection spreads from limb to limb, the whole tree 

 becomes diseased, and eventually perishes. In Gloucestershire, 

 England, so many apple-trees were destroyed by these lice in 

 the year 1810, that it was feared the making of cider must be 

 abandoned. In the north of England the apple-trees are 

 greatly injured, and some annually destroyed by them, and in 

 the year 1826 they abounded there in such incredible luxuri- 

 ance, that many trees seemed, at a short distance, as if they 

 had been whitewashed. 



Mr. Knapp thinks that remedies can prove efficacious in 

 removing this evil only upon a small scale, and that when the 

 injury has existed for some time, and extended its influence 

 over the parts of a large tree, it will take its course, and the 



