64 The American Naturalist. [January, 
which every alternate tree is sprayed. A conclusive experiment 
necessitates an orchard of considerable size,—one half to be sprayed 
and the other half either to be jarred or left untreated,—or else two 
orchards near together, with a similar difference in treatment. Of 
course, by the every-other-tree method, results of some value may be 
obtained, but the conditions of the commercial orchard, where all the 
trees are sprayed, are far from being reached.”’ i 
So far as entomologists are concerned, the discussion of this subject 
appears to have begun in 1870, when Dr. C. V. Riley wrote the follow- 
ing paragraph upon it :? 
Mr. G. M. Smith, of Berlin, Wisconsin, . . . recommends Paris 
green for the Plum Curculio. Even if the uniform application of 
such a poisonous drug on large trees were practicable, it would never 
succeed in killing one Curculio in a hundred. Paris green kills the 
leaf-eating beetles by being taken internally with the leaves; but the 
Curculio, with its snout, prefers to gouge under the skin of the fruit, 
and only exceptionally devours the leaves. Yet, notwithstanding the 
palpable absurdity of the remedy, it has very generally passed from 
one journal to another without comment.”’ 
Fifteen years later Dr. Riley delivered an address before the Missis- 
sippi Valley Horticultural Society, in which, ‘‘in giving his experience 
as to the feeding habits of the beetles, he urged experimentation with 
the arsenites in this direction as promising fair results, though in the 
very nature of the case not as satisfactory as in the case of the Codling 
Moth.” s ee 
In November, 1888, Dr. Riley, in reviewing a bulletin by Professor @ 
A. J. Cook, in which the latter reports successful results with the 
arsenites as Curculio destroyers, wrote : ee 
‘‘ We have long felt that they [the arsenites] might be used with : | 
benefit for this purpose, but from the nature of the case we have ae 
ticipated less good than in the case of the apple worm, and Professor 
Forbes’s experiments, and some unpublished experiments which wê 
have had made by Mr. Alwood, confirm this view.” . 
Shortly after this Dr. Riley read an elaborate paper concerning the 
Plum Curculio before the American Pomological Society, at its meet- 
ing in February, 1889, in which the use of arsenical sprays was especially _ 
discussed. is article, in substantially the same form, was also m- 
corporated in the memoir upon the Plum Curculio published by Riley 
* Third Report State Entomologist Missouri, p. 18. i 
* Riley. Rept. Am. Pom, Soc., 1889, p. 31. 
* Insect Life, November, 1888, Vol, I., p. 123. 
