73 



latitude of the extreme southern point of Illinois, as "utterly destroy- 

 ing the best apple-orchards in that county, starting on the trunks of 

 the trees, spreading rapidly on the branches, and then on the apples — 

 killing large trees in two years." {Rural World, October 15, 1866.) 

 I heard no complaints of this insect being at present at all trouble- 

 some near Cobden, South Illinois; but at some future day it may 

 likely enough make an irruption upon the pear orchards of Southern 

 Illinois in full force. 



I observe that on all my apple-trees, which were infested a year 

 or two ago by Harris's Bark-louse, this native species is being gradu- 

 ally supplanted by the improved and highly-developed species from 

 the other side of the Atlantic; just as the White Man is supplanting 

 the Eed Man in America, or as in New Zealand the European House- 

 fly (Musca domestica, Linnseus) and the Brown Xonvay Eat (Mm 

 decumanus, Linnasus) are driving out the Native Fly and the Native 

 Eat. (See Spencer's Principles of Biology, I, p. 389.) It is preyed 

 on by the same Mites as the other kind, and, being so closely allied to 

 it, must be attacked on the same principles and with the same weapons. 



INSECTS INFESTING THE APPLE.— On the Eoot. 



CHAPTER X. — The Apple-root Plant-louse, (Pemphigus pyri. Fitch,) com- 

 monly but incorrectly called in Illinois "The Woolly Aphis." 



This insect has been very generally confounded with the true 

 "Woolly Plant-louse" or "Woolly Aphis" (Eriosoma lanigera, Haus- 

 mann), which, so far as is known at present, occurs only on the At- 

 lantic seaboard, though it may perhaps eventually work its way West- 

 ward into the Northern parts of the Valley of the Mississippi. It is 

 very true that both insects are "woolly," inasmuch as they both secrete 

 a woolly or cottony substance from the general surface of their bodies, 

 and both are "Plant-lice," inasmuch as they both belong to the Aphis 

 family; but they differ in their native country, they differ in the 

 structure of their wing-veins and consequently in the genus to which 

 they are referable, and they differ very widely in their habits. 



The true "Woolly Plant-louse" is an imported insect, having been 

 in reality introduced into America from Europe though, singularly 

 enough, it was misnamed in England "the American Blight," when 

 it was first noticed in that country towards the close of the last cen- 

 tury, and was erroneously supposed to have been introduced there from 

 America. It is now, however, pretty clearly ascertained to have ex- 

 isted on the continent of Europe for time immemorial, and it probably 



