280 APPLE. 



appearance of a white film growing at the bottom of the 

 crevices where a few of them are kirking. Where there are 

 many the spot appears as if a knot of cotton-wool was sticking 

 to the bough, or even hanging down in pieces several inches 

 in length, ready to be wafted by the first gust of wind, with 

 all the insects in it, to a neighbouring bough. 



The " BHght " is chiefly to be found in neglected Apple 

 orchards. Its head-quarters are in crevices in the bark, or in 

 hollows where young bark is pressing forward over the surface 

 where a bough has been cut off, or broken by accident so as 

 to leave a shelter of the old dead bark outside ; it may, how- 

 ever, be found on almost every part of the tree into which the 

 Aphis can pierce with its sucker ; and the harm caused by 

 the attack is not only from the quantity of sap drawn away 

 from the bark or young shoots, but also from the diseased 

 growth which is thus set up. The bark is at first not much 

 affected by the punctures, but the woody layers beneath 

 become soft, pulpy, and swollen. The cells and fibres divide 

 and subdivide, and the bark splits open over the swelling, 

 showing the tissue beneath, which is thus exposed for a fresh 

 attack. 



At the end of summer these watery swollen growths dry up 

 anddie, and thus form deep cracks. With the return of spring 

 (as in other cases of injmy) a new growth forms round the 

 dead part, and this soft tissue is ready for the young Aphides. 

 Thus, from the swollen diseased growth caused partly by the 

 Aphides, partly by the -natural atl^empts of the tree to repair 

 damage, a constantly increasing diseased mass arises, which 

 shelters the insects in its crannies, and finds food for them in 

 its young hypertrophied formations. 



The above note of the progress of diseased growth is from 

 the paper by M. Prillieux in ' Comptes Eendus ' for April, 

 1875. 



The " American Blight " Aphis is stated to have been imported 

 from America in 1787, but whether this is a fact appears 

 somewhat uncertaiu. It may be known at a glance from the 

 common Apple Aphis (scientifically Aphis mali), which is 

 injurious to the leaves, by the white wool with which it is 

 more or less covered, and from which it takes its name of 

 " Woolly Aphis," and examination of the wings through a 

 magnifying-glass will show that they are differently veined. 

 A strong vein runs down the fore wing near the front edge, 

 and from this three veins turn ofi' towards the hinder edge. 

 The third of these veins from the body has only one fork in 

 the American Blight or Woolly Aphis. By this the Sckizo- 

 neurince, to which division it belongs, are distinguished from 

 the Aphidince, which have tico forks to this vein (as in Hop 



