102 LEAFAGE CATERPILLARS, 
Department of Agriculture, Ontario, Canada, who assisted us greatly 
by his advice, noted :—‘‘ One great point is to insist on the mixture 
not being made too strong; one pound to two hundred gallons I find 
very useful, and I never use stronger than one pound to one hundred 
and twenty gallons.’’—(J. F.) 
Dr. J. B. Smith, in his work above referred to, notes that Paris- 
green, ‘‘ for most insects, will be effective when applied in liquid form 
at the rate of one pound in two hundred gallons of water.”’ 
In mixing and in the use of Paris-green as a fluid dressing, it is to 
be remembered that it does not dissolve in water, it is only held in 
suspension. It is very heavy, and will keep sinking to the bottom of 
the barrel or machine unless constantly agitated, therefore the mixture 
should be constantly stirred, and the barrel well washed out after being 
refilled several times, otherwise the residue will keep accumulating, 
and the mixture be too strong near the bottom. 
With regard to method of application of the spray.—This should be 
thrown so finely as to reach all parts of the tree and both sides of the 
leaves, and coat the leaves as with a fine dew, but it should not be 
allowed to run down and drip. As soon as dripping begins spraying 
should cease. 
Also, spraying should not be done whilst the trees are in blossom, and 
sprayings should not be given in rapid succession. Several days 
should elapse between, unless, of course, as may easily happen in 
difficulties of first experiments, the spray was manifestly so weak that 
the previous application counted for nothing. The effect of the Paris- 
green on the caterpillars does not always show directly, and it is 
undesirable to waste labour and material where the work is already 
done, and only requires a day or two to show it. 
With regard to the nature of Paris-green, or emerald-green, as it is 
sometimes called, it is an aceto-arsenite of copper, and of a poisonous 
nature, or, if by mishap swallowed in any large amount, is (as we see 
in the case of the insects feeding on the poisoned leafage) a deadly 
poison. It should never be used to fruit or to vegetables to be used for food. 
Cautions to be observed in the use of Paris-green.—The bags should 
be labelled Porson and kept locked up, and especially kept safely out 
of the way of children, who might be attracted by the beautiful colour. 
Workers with the powder should not allow it to settle in any sore 
or crack in the skin of the hands, or stir it about unnecessarily with 
the hands ; and they should be very careful not to breathe in the powder 
through mouth or nose whilst measuring or mixing it. It can be 
procured from Messrs. Blundell & Spence, Hull, in damped condition, 
which saves much risk from inhaling the powder. Also it is now 
procurable in much finer powder than was the case at first, and as 
this goes much further in using than the coarser grain, this must be 
