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THE ECONOMIC VALUE OF PARASITES AND PREDACEOUS INSECTS. 
By JOHN B. SMITH, Sc. D., New Brunswick, N. J. 
At the very outset I wish to disclaim all intention either of pro- 
ducing a treatise on parasitism in general or disputing the importance 
of parasites in nature. No one can realize more than I do how much 
parasites maintain the balance and check the increase of injurious spe- 
cies. Iam perfectly aware that were it not for parasites many an insect 
would become so abundant that certain crops could not be satisfactorily 
grown. Fully realizing, therefore, the place and importance of these 
parasites I feel at the same time that their economic value has been 
grossly overestimated; in fact I am almost ready to say that parasites 
have no real economic value to the agriculturist. This sounds like a 
very radical statement, and perhaps I do not mean it in the fullest 
sense of the terms that I have used; but I would not much modify the 
sense of the language. The “life history” of an insect is incomplete 
until we know not only how it lives and upon what it feeds, how it 
transforms, and the duration of its various stages, but also what spe- 
cies prey upon it, and to which it furnishes sustenance in one or the 
other of its stages. We are therefore right in our studies of the “life 
history” of injurious insects in studying also the parasites that prey 
upon them. Weare right also in publishing the results of our work, 
including the descriptions of the parasites. We are right in calling the 
attention of the farmer to the fact that the injurious species are very 
largely kept in check by either parasites or by predaceous insects; but 
we are wrong in leading him to suppose that either parasites or pre- 
daceous insects will control the injurious species for him. Yet the 
tendency of the language used in many cases by entomologists, and 
more often by those who are not entomologists, has suggested the 
possibility that injurious species may be controlled by either parasites 
or natural enemies without very much work on the part of the farmer. 
The impression is current that it will be possible to use natural means 
to exterminate injurious insects, and I have been asked frequently dur- 
ing the past two years, by farmers that may be considered as fully equal 
in intelligence to the best in the land, those who read and usually 
understand, why I did not make some effort to cultivate or import 
parasites or natural enemies of our common injurious insects. Of 
course these questions all grow out of the remarkably successful 
experiment made by Dr. Riley in the importation of the Australian 
Vedalia cardinalis to exterminate the imported Icerya purchasi, and I 
have decided to bring upthis subject for discussion at the present meet- 
ing in order that possibly a little more definite light canbe obtained 
upon the exact place of parasites and predaceous insects in economic 
entomology. It needs no argument on my part to prove that nature 
