ACTING STATE ENTOMOLOGIST. 
47 
is pretty good evidence, that such substances, if spread thinly over a great part of the 
surface of a tree, and even if spread over its entire surface, are not perceptibly injurious 
to it, or at all events not invariably so. 
5th. Scrubbing the limbs of a tree with a stiff brush, shortly after the Bark-lice 
have hatched out, will destroy them and remove them from the infected surface ; but 
no such mechanical appliance can remove or otherwise affect the perfected scale, simply 
because it sticks too tight, and is of too hard and solid a texture. 
6th. By scraping the bark with the edge of a knife or other such tool, even the 
perfected scale may at any time of the year be removed and destroyed. 
To give all the details of all the experiments that I have made, bearing upon the 
above general rules, would occupy entirely too much space and only weary the reader. 
But I maybe pardoned, perhaps, for giving the details of a few of them, and for 
particularizing several facts obtained from other sources, in order that it may be 
seen upon what kind of evidence my general conclusions are based. Each statement 
is numbered, so as to correspond with the six general laws already laid down. 
Statement 1st.—On June 12th, 1867, being eight days after the Bark-lice had 
hatched, and probably about four or five days after they had become permanently sta¬ 
tionary, I prepared some tobacco-water, by boiling for three hours one part, by measure, 
of common smoking-tobacco and seven parts of water, renewing the water as it boiled 
away. This fluid I squeezed with a sponge over a badly infested branch, so as to wet 
the whole of it thoroughly both above and below, using no brush or swab of any kind, 
so as absolutely to eliminate the effects of mechanical friction upon the young Bark- 
lice. I had previously pruned the branch so as to cut off all communication with 
neighboring branches, except at its origin ; and of course I labeled it and registered 
it in my Journal. From time to time through the summer I examined it, and found 
the young Bark-lice apparently growing as vigorously as on ihe rest of the tree. 
On October 30th I cut off a portion of it, one foot in length and averaging one-third 
of an inch in diameter, and examined the scales one by one under a lens. This piece, 
be it observed, was so distant from the origin of the branch which I had washed with 
the tobacco-water, that it was very improbable that any amount of young Bark-lice 
could afterwards have crawled out on to it from the other parts of the tree, even sup¬ 
posing them to have retained their original powers of locomotion. I found, on examining 
it, at least 200 scales containing good, plump, healthy eggs, and about 400 that had 
either been completely gutted by the Mites, or were undergoing that process. There 
were about seven or eight scales from which no “anal sack” had developed; these 
might possibly have been larvae killed by the tobacco-water, but I took them for scales 
from which males had developed ; for this is about the proportion of such scales usually 
met with in branches that have not been medicated in any way. The old dead last 
year’s scales upon this piece of a branch, I did not think it necessary to count. Hence, 
I infer that strong tobacco-water cannot kill the Bark-louse at any period of its exis¬ 
tence; for if it has no effect upon it when it is in the tender larva state, a fortiori it will 
have no effect upon the matured or partly matured scale. 
That most accurate observer, Dr. Mygatt, arrived at similar results. “When I had 
ascertained,” he says, “the hatching season, I fondly hoped that the decoctions of 
quassia and tobacco, which I have for several years used on the Plant-lice, (Aiohides), 
would also destroy the young Bark-lice ([Coccids /) but in that I was doomed to be 
sadly disappointed on trial.” {Trans. III. State Agr. Soc., I., p. 516.) 
Statement 2d. —On June 12th, 1867, I prepared a solution of common saleratus, 
