194 INSECTS INJURIOUS TO VEGETATION. 



are deposited in the crotches of the branches and in the chinks of 

 the bark at or near the surface of the ground, especially if there 

 are suckers springing from the same place. The young, when 

 first hatched, are covered with a very short and fine down, and ap- 

 pear 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 distinct, 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 testi- 

 mony 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 destitute 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 through- 

 out an extensive orchard. The numerous punctures of these lice 

 produce on the tender shoots a cellular appearance, and wherever 

 a colony of them is established, 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 hce 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 luxu- 

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

 been whitewashed. 



Mr. Knapp thinks that remedies can prove efficacious in re- 

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



