ACTING STATE ENTOMOLOGIST. 
51 
solve the tar. The mixture is put on with a brush at any time during the winter or 
early spring, and has the appearance of a varnish. It has the advantage over the alka¬ 
line washes, used on the young insects, that it can he applied to all parts of the tree 
without the least injury to the shoots or buds, while it is death to the insect. His trees 
are nearly free of the insect, and have become vigorous and fruitful.” (Transactions 
Illinois State Agricultural Society , V. p. 190.) The tar is probably inert here, except so 
far as it dilutes the oil, and it is in reality the linseed oil that kills the eggs. 
In 1866 Mr. Cavanach, a market-gardener residing at Brooklyn, New York, said that 
he “had succeeded in destroying the scale-insect by the use of kerosene, without injury 
to the trees.” {New York Sem. Tribune , March 16, 1866.) And subsecpiently he states 
as follows :— “We use kerosene regularly every year to kill the scale-insect and other 
parasites upon our plants and trees without injury to them ; and it has frequently been 
stated that crude petroleum has been used for the same purpose with good effects. Gas 
tar has proved injurious.” {Ibid. March 30, 1866.) Two years afterwards the same man 
speaks in the following manner of petroleum : — “If anyone wants to kill his trees, let 
him use petroleum ; yet it is beneficial in a diluted state when applied to shrubs and 
plants to keep off insects, but it is death when applied to the roots.” {Ibid. Jan. 10, 
1868.) Whether these observations are intended to apply to kerosene as well as to 
petroleum, is more than I can say. 
At the Meeting of the Iowa State Horticultural Society, Oct. 19, 1867, Mr. J. L. Budd, 
a fruit-grower residing at Shellsburg, Benton Co., Iowa, stated that he “had found 10 
parts of benzine and 4 of soap the best remedy against Bark-lice.” The benzine would 
in all probability be effectual at any time of the year ; but, as I think I have shown, the 
soap would be useless, except early in the summer and except also by its diluting the 
strength of the benzine. 
Finally, Dr. Pennington, of Sterling, Whiteside Co., Illinois, told me in 1867, that he 
had applied pure petroleum to the trunks of about 100 apple-trees, infested by the Oys¬ 
ter-shell Bark-louse, and to about one half of such of their limbs as were 1 % inches and 
over in diameter ; and that he can perceive no injurious effects. Before applying the 
petroleum, he pruned the trees well. 
I think that there can be no doubt whatever, that petroleum, kerosene, benzine, lard, 
and generally any kind of animal or vegetable oil, w r ill kill Bark-lice at any time of the 
year, though all kinds of watery infusions fail to have any effect upon the matured 
scale. The reason is obvious. The eggs under the scale can only be killed by some 
substance capable of reaching them through the protecting scale, which is glued too 
firmly and closely to the bark to allow of anything penetrating underneath it. Now, 
nature has made the scales rain-tight; but, as we have no showers of oil, she has not 
thought it necessary to make them oil-tight. Hence, oily substances will soak through 
the scale, and reach the culprit eggs ; but watery infusions are incapable of doing this. 
Whether some or all of these oily applications may not be more or less injurious to 
vegetable life, is a much more doubtful and disputable question. I saw an account in 
the New York Tribune several years ago, of a whole orchard being killed by applying 
“tanners’ oil” to it, whatever that kind of oil may be. Perhaps it might have been 
applied in exorbitant quantities. Again : I have known a plum-tree killed by saturat¬ 
ing a large cloth with kerosene, and wrapping it round the butt, under the ridiculous 
idea that the Curculio could thus be prevented from getting at the plums. Again : 
Mr. Mitchell, of Pennsylvania, writes to the New York Farmers’ Club, that having been 
advised in the Proceedings of that Club to apply kerosene with a feather to young 
