66 The American Naturalist. [ January, 
“Clearly, if the question of comparative efficiency raised in the 
paragraph quoted above is to rest on a rational basis, it must be put in 
something like the following form: Is the deposition of Curculio eggs 
prevented (through the destruction of the parent beetles) by the appli 
cation of arsenites to plum trees in as great a proportion as Codling 
Moth larvz are destroyed by the same applications to apple trees? It 
is probable that each female Codling Moth and Plum Curculio deposits 
on an average about fifty eggs, so that, reduced to figures, this question 
resolves itself into the following: Is the application of the arsenites as 
likely to kill one adult female Curculio, feeding indiscriminately over 
a large amount of poisoned surface, before it has deposited eggs, as it 
is to kill fifty Codling Moth larvæ before they enter the apples. 
“In order to get at field conditions, suppose that in an orchard of 
1,000 apple trees there was a female Codling Moth to each tree, and 
that in an orchard of 1,000 plum trees there was a female Curculio to each 
tree. It is usually estimated that seventy-five per cent. of the fruit liable 
to injury by the Codling Moth is saved by spraying ; so it becomes a ques- 
tion of whether spraying will be as likely to destroy the equivalent of 
750 female Curculios before their eggs are laid, as it will to destroy 3,759 © 
Codling Moth larve after they hatch. The answer to this question 
will be found along the experimental rather than the a priori road.” 
It will readily be granted, from the explanation already given, that 
if the case be restricted to a single tree, or a few trees in the midst do 
other trees liable to injury by the Curculio, the odds would be in favor a 
the Codling Moth, at least for the first brood, but on a commercial 
scale the above reasoning must apply. Raa 
The writings of Professor A. J. Cook form an important part of w 
discussion upon this subject, During the first six or seven years of bn - 
last decade he frequently expressed the opinion that the Curculio could ie | 
not be destroyed by the arsenites. For instance, in 1886 he is on ou 
record as saying : | 
“Paris green, kerosene emulsion, and other poisons are of no avail 
against the Curculio. He will not eat them.” ° : 
In 1887 Professor Cook took up the subject in an experimental ee 
The only record of the season’s work is the following paragraph : t 
“ Paris green, in the proportion of one tablespoonful to six gallons 
of water, was very thoroughly sprayed upon four plum trees, May 10°" 
The petals had all fallen, but the dried calyces still clung to the ge 
On August zoth the trees were visited, when it was found that the t"? 
8 Report Mich. Board of Agriculture, 1886, p. 141. 
® Report Mich. State Board of Agriculture, 1887, p. 40. 
