OF THE FAEM Al^B GAEDEK. 



149 



Illinois, obseryation has shown that it does not exist in 

 the southern half of the same State. 



As the female Bark-louse is only capable of motion for 

 two to three days at the most, after which time she 

 becomes as permanently fixed for the rest of her life, as is 

 the tree on which she is fastened, it may puzzle some to 

 diA^ne how this insect spreads from tree to tree, and place 

 to place. That it is transported to distant places, mainly 

 on young trees, there can be no doubt, and there are 

 various ways in which it can spread from tree to tree in 

 the same orchard, though it can only thus spread during 

 the few days of its active larval state. 



Though essentially belonging to the Apple Tree, this 

 Oyster-shell Bark-louse, is found upon the Currant, the 

 Plum, and the Pear. I have seen the scales fully 

 developed, and bearing healthy eggs on the fruit of the 

 AYhite Doyenne Pear, of the Transcendent Crab, and of 

 AYild Plum [Prunus Americana)', and, though on the 

 hard bark of a tree, we cannot judge of the amount of 

 sap they absorb, it is quite apparent on these soft fruits, 

 for each scale causes a considerable depression from the 

 general surface. 



Remedies. — If an orchard is once attacked before the 

 owner is aware of it, much could be done on the young 

 trees by scraping the scales off in winter, but on large 

 trees, where it is difficult to reach all the terminal twigs, 

 this method becomes altogether impracticable, and it 

 will avail but little to cleanse the trunk alone, as most of 

 the scales containing living eggs will be found on the 

 terminal branches. Alkaline washes, and all other 

 washes, except those of an oily nature, such as petroleum 

 and kerosene, are of no avail when applied to the scales, 

 for the simple reason that they do not penetrate and 

 reach the eggs which are so well protected by these 

 scales; and it is very doubtful whether any solution can 

 be used, that is sufficiently oily to penetrate the scales 



