33 ENTOMOLOGY 



or botanist, or he may have the whole theory and practice of agriculture 

 at his tongue's end, and at his fingers' ends as well, and yet be without 

 knowledge or resources when brought face to face with a new practical 

 problem in economic entomology. The subject is essentially that of 

 the relations of these things to each other; of insect to plant and of plant 

 to insect, and of both these to the purposes and operations of the farm, 

 and it involves some knowledge of all of them. 



"As far as the entomological part of the -subject is concerned, the 

 chief requisites are a familiar acquaintance with the common injurious 

 insects, and especially a thorough knowledge of their life histories, to- 

 gether with practical familiarity with methods of entomological study 

 and research. The life histories of insects lie at the foundation of the 

 whole subject of economic entomology; and constitute, in fact, the 

 principal part of the science; for until these are clearly and completely 

 made out for any given injurious species, we cannot possibly tell when, 

 where or how to strike it at its weakest point. 



"But besides this, we must also know the conditions favorable and 

 unfavorable to it; the enemies which prey upon it, whether bird or in- 

 sect or plant parasite; the diseases to which it is subject, and the effects 

 of the various changes of weather and season. We should make, in fact, 

 a thorough study of it in relation to the whole system of things by which 

 it is affected. Without this we shall often be exposed to needless alarm 

 and expense, perhaps, in fighting by artificial remedies, an insect already 

 in process of rapid extinction by natural causes; perhaps giving up in 

 despair just at the time when the natural checks upon its career are 

 about to lend their powerful aid to its suppression. We may even, for 

 lack of this knowledge, destroy our best friends under the supposition 

 that they are the authors of the mischief which they are really exerting 

 themselves to prevent. In addition to this knowledge of the relations 

 of pur farm pests to what we may call the natural conditions of their life, 

 we must know how our own artificial farming operations affect them, 

 which of our methods of culture stimulate their increase, and which, if 

 any, may help to keep it down. And we must also learn where strictly 

 artificial measures can be used to -advantage to destroy them. 



"For the life histories of insects, close, accurate and continuous ob- 

 servation is of course necessary; and each species studied must be fol- 

 lowed not only through its periods of destructive abundance, when it 

 attracts general attention, but through its times of scarcity as well, and 

 season after season, and year after year. 



"The observations thus made must of course be collected, collated 



