36 
FIRST ANNUAL REPORT OF THE 
and found them worthless. I know several orcliardists troubled by this vile pest, who 
have arrived at the conclusion, after experimenting in vain with a dozen different 
remedies, that it is no use trying to fight it, and that their apple-trees are irretrievably 
ruined and “ gone up.” 
As with all other Noxious Insects, before we can fight this Bark-louse understandingly, 
it is necessary to know who and what she is, how she is propagated from year to year, 
how she spreads from one tree to another, and what are her peculiar habits and mode of 
life. I put her in the feminine gender, because, witho.ut a single exception, all the 
scales that come under the notice of the fruit-grower contain eggs under them, and are 
consequently all of them females. And here, at the very outset, the inexperienced 
observer is often involved in error and confusion. There are two perfectly distinct 
Bark-lice, with different habits and modes of life, commonly found in Illinois on the 
apple-tree, which are popularly confounded together — by a very indefinite application 
of the Definite Article — under the appellation of “ THE Bark-louse.” The first — 
which is the one with which we are now more immediately concerned— is a species 
introduced into the Eastern States more than seventy years ago from Europe, but which 
only penetrated into Illinois about fifteen years ago ; occupying at first the districts 
bordering upon Lake Michigan, where it committed terrible ravages, and thence spread¬ 
ing gradually Westward and Southward, till only a few years ago it touched the 
Mississippi River. The second— which we may call “ Harris’s Bark-louse,” and which 
will be referred to more fully in the following Chapter —is a native-American species, 
and has existed for time immemorial both in the East and in the West, its original home 
being our native crab-trees, upon which I observed it many years ago. The first cannot 
thrive except in comparatively northern latitudes; for even in Champaign Co., in 
Central Illinois, as I am informed by Mr. M. L. Dunlap (“ Rural ”), although it has been 
long known there, yet it does not increase so as to be at all formidable ; and, as I was 
told in Southern Illinois, it actually dies, when it is introduced there upon young apple- 
trees brought from the north.* Harris’s Bark-louse, on the contrary, flourishes 
vigorously, to my certain knowledge, so as to be a great pest in the latitude of Phila¬ 
delphia, which is somewhat south of Champaign ; and in Missouri it probably extends 
to a point at least 180 miles further south, where it does a great amount of damage. It 
occurs also in considerable numbers throughout the whole State of Illinois, but is 
nowhere anything like so destructive as the Imported Species. Indeed almost all our 
worst Noxious Insects have been imported from the Old World, and are far more des¬ 
tructive than the corresponding species indigenous to North America —a curious fact 
which I have explained and illustrated at some length in the Practical Entomologist , 
(Vol. I. No. 12.) 
“But,” the reader will ask, “how am I to distinguish these two Bark-lice, the one. 
* Since the above was written, I have received the Oyster-shell Bark-louse from Mr. J. Huggins, of 
Macoupin county, Central Illinois, with a statement that it swarms at Shipman, in that county, on two 
trees that were imported eight years ago from New York, though “ the other trees in the orchard are 
not yet seriously affected.” On examining the infested twigs sent by Mr. Huggins, I found that about 
19-20ths of the eggs under the scales had been destroyed by the same Cannibal Mite that, as will be after¬ 
wards shown, operates upon them in Northern Illinois. Now, in North Illinois, the largest proportion 
of eggs, that I ever found to be destroyed by this Mite, was only two-thirds. Hence, I infer that the 
Mite is a far more efficient check upon the multiplication of this Bark-louse in Southern than in North¬ 
ern latitudes. Certainly if this Bark-louse had been introduced into any county in North Illinois eight 
years ago, it would have been all over the county long before now; whereas, in Macoupin county it 
seems to have scarcely spread beyond the two trees on which it was originally imported eight yeai'S ago. 
