24 FIFTH ANNUAL REPORT 



of one who makes it his especial duty to investigate the subject ? 

 There are two grand methods of counterworking a particular noxious 

 insect: 1st, Prevention — i. e., guarding against the advent of the evil 

 by proper foreknowledge, and prophylactic steps; 2d, Cure — i. e., 

 the destruction of the pests, in one way or another, when once they 

 are upon us. The last method consists of two distinct plans of ac- 

 tion — that of killing directly by hand-picking, machinery, or the 

 application of destructive substances to the plants or animals af- 

 fected; and that of causing them to be killed by encouraging their 

 natural enemies. 



Prevention. — The first method — prevention — is by far the most 

 satisfactory. 



The feathery snow-flake, on its serial course, 



Is made, with ease, to vanish by a breath ; 

 To avalanche augmented, 'tis the source 



Of dire calamity — inevitable death. 



It is an undeniable fact that many of the most troublesome weeds 

 of American agriculture, as also some of its very worst insect enemies, 

 have been imported among us from Europe; and the list of such spe- 

 cies, given in my second report, might be greatly extended. The sin- 

 gle case of the Rape Butterfly {Pleris rapm) will serve to show how 

 rapidly these foreigners multiply, and how injurious they become 

 when unattended by the natural enemies which keep them in check 

 in their native homes. Introduced at Quebec, Canada, in 1856, it has 

 now spread over Canada West and most of the New England States, 

 as far south as Baltimore, and nearing the eastern limit of New York. 

 It sweeps the cabbage crop at all points it reaches, and caused, in 

 1871, a loss of $500,000 in the vicinity of New York City alone, if we 

 are to believe the New York Tribune. 



Now, there can not be the least doubt but that with the proper 

 precautionary steps many of these immigrants from a foreign land 

 need never have been introduced, or might have been stamped out, 

 on first arrival, and kept from spreading over our fair country.. 



But insects not only spread from one country to another : they 

 spread from State to State, from county to county, and from orchard 

 to orchard ; and in very many instances, this spread from place to place 

 is very easily prevented, but unfortunately, just as easily, and more 

 often, aided by man. Quite a number of our most noxious species 

 would scarcely spread fifty miles in a century, were it not for the aid 

 which man in his carelessness gives them. Some are active but a sin- 

 gle day in the year; some move slowly under ground; some n ever 

 quit the trees on which they are born ; while still others are apterous 

 in the female sex, and have otherwise very feeble ambulatory power. 



In checking the spread of noxious insects does not consist the 

 only way to prevent their injuries. We can also take advantage of 

 their weak points, or nip the evil in the bud. Thus, when we know 



