THE APPLE-TREE LOUSE. 243 



the spring of the year like little specks of mould on the 

 trees (Fig. 92X As the season advances, and 



. s . . . . T 



the insect increases in size, its downy coat be- 

 comes 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 



O 



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, antenna?, suck- 

 er, 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 des- 

 titute 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, wlu'ch 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 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 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 annu- 

 ally destroyed by them, and in the year 1826 they abounded 

 31* 



