ACTING STATE ENTOMOLOGIST. 
53 
writes that the cold winter of 1863-4 had effected no diminution of the numbers of the 
Bark-lice, even in that high latitude. 
As to what is a very current opinion amongst many of our most intelligent fruit¬ 
growers, namely, that it is only diseased, unhealthy, and badly-cultivated trees that 
suffer materially from Bark-lice, I am satisfied that this is an error. My own trees grow 
in garden soil, dug originally two spit deep, with a porous gravelly subsoil two or three 
feet below the surface, manured moderately every year with old thoroughly rotten cow 
manure, and cultivated through the summer ; and the chief difficulty that I have with 
them is, that they grow too exuberantly and run too much to wood. Yet, in spite of 
palliatives applied from time to time, and in spite of my little friends the Mites, the 
Bark-lice are steadily gaining on me ; and unless I make a vigorous onslaught on them 
before long, they will probably in the end overrun all my trees. The truth seems to be, 
that, after a certain number of years, the Mites and Insects that prey upon the Bark- 
lice become so numerous as to check them up permanently. And thus we can account 
for the notorious fact that in those northern regions, where only the Oyster-shell Bark- 
louse can thrive — as for example in Northern Illinois and Wisconsin — it is death upon 
apple-trees, for 6 or 8 years after it is introduced, but afterwards sobers down, and, 
though still a grievous pest, becomes, comparatively speaking, innocuous. 
Before concluding this long chapter, I ought to caution the reader against a very 
prevalent, but a very delusive idea. People are perpetually reasoning upon the assump¬ 
tion, that any fluid substance, that they may apply to the limbs of a tree, is taken up 
by the sap and carried to the remotest twig ; as if plants, like the higher animals, had 
a complete circulatory system of veins and arteries; whereas every botanist knows that 
it is no such thing. Whatever you apply to your tree to kill the Bark-lice, whether 
soapy solution or oily fluid, can only kill those insects that it actually touches, and will 
not be absorbed by the sap and carried unchanged to other parts, so as to kill the Bark- 
lice upon those parts. If it were otherwise, the apples on a tree that had been soaped 
would taste of soap, and those on a tree that had been treated with kerosene, would 
taste of kerosene. But that this is not so, every one may satisfy himself by an easy 
experiment, if he does not, as I do, know the fact already. Possibly, to a very limited 
extent, such substances as those referred to above may be absorbed by the cellular sys¬ 
tem of the tree ; but even in that case they will undergo chemical changes, which will 
totally unfit them for destroying insect life. To believe that pure kerosene, or pure 
soap, applied to one end of a tree, will pass in the very same chemical form to the other 
end of it, is as absurd as to believe that liquid manure can be taken up by the roots 
of a tomato-plant, and pass in that form and without any chemical change into the ripe 
tomatoes. 
CHAPTER IX. — Harris’s Bark-louse. (Aspidiotus Harrisii, Walsh.) 
I have discussed the Natural History of the Oyster-shell Bark-louse at such exorb i 
tant length, that it will not be either necessary or advisable to dilate upon that of this 
species, further than to point out the very remarkable characters in which it differs 
from the other. 
1st. The difference in the shape and color of the scales, and in the color of the eggs, 
has been already explained. (See above, page 37.) The eggs hatch out at almost 
exactly the same date, (June 5th, 1867,) but, instead of the young larvae being yellowish 
white, and soon afterwards becoming covered with a white powdery bloom, so as to 
form conspicuous although very minute white objects on the bark, they are blood-red 
