240 HEMIPTEEA-HOMOPTERA. 



damson is called variety Mahaleh, having slightly different pro- 

 jections at the base of the antennse, but is not specifically 

 distinct. Thus we see there are two ways of living in this 

 species — upon the hop entirely, and also by migrating between 

 the hop and the prunes. Many Aphides have this migratory 

 habit, as seen in P. humuli. 



American Blight or Woolly Aphis (Schizoneura lanigera). 



The Woolly Aphis is one of the most widespread plant-lice 

 affecting fruit-trees. Its presence can easily be detected by the 

 quantity of white cottony wool produced by the larvae and 

 females. We often, especially in west-country orchards, see this 

 white excretion hanging from the trees in great festoons. The 

 trees suffer severely. Apple-trees are those that suffer most, but 

 pear-trees may also be attacked. These plant-lice cause cankered 

 growths to appear on trunk and boughs ; the new wood is their 

 favourite seat of war, where they can easily plunge their beaks 

 into the soft rind. This wound usually ends by spHtting, deep 

 cracks and crevices being formed, in which the culprits seek shel- 

 ter later. Growth is checked ; the crop does not mature, and 

 often the trees fail under the attack. If we examine this white 

 wool, we shall see that it proceeds from the backs of the lice and 

 females, as fine threads of wax. Amongst this excretion we ob- 

 serve the orange-coloured lice, which get blown from tree to tree 

 with the wool by the wind, and even from orchard to orchard. 

 The adult females are slaty-grey to plum colour, and have no 

 cornicles; these adults secrete but little wool, but are never- 

 theless well protected by mealy powder and little globules of an 

 oily nature. In July and August there may appear winged 

 females, and in autumn an oviparous female and male sometimes 

 occur. Very few eggs are laid, however ; each oviparous female, 

 I fancy, only laying a single black ovum on the apple-tree, so as 

 to secure the continuity of the species. The majority pass 

 the winter as mother-females in crevices in the bark and at 



