PREFACE 



This little book has been written for beginners who are 

 willing to take some pains to acquire a practical knowledge 

 of insects, and are specially interested in the application 

 of entomology to agriculture, horticulture, and forestry. A 

 practical purpose is, in my opinion, not a hindrance but a 

 powerful motive to the acquisition of scientific knowledge. 

 If not too narrowly prosecuted, the practical purpose may be 

 a means of distinguishing knowledge which is really useful 

 from knowledge which is merely curious. I feel sure that 

 it is much more likely to exercise a wholesome influence on 

 natural history than collecting and naming, which have been 

 far too exclusively attended to for many years past. 



I have tried to meet the wants, not only of those who are 

 concerned with insect-ravages, but also of those who seek to 

 inquire into the works of nature. Injurious and useful insects 

 are as full of contrivance, and as beautifully equipped for the 

 struggle of life, as any others. Since they are among the 

 commonest species, they can be easily and profitably studied 

 by those who have no purpose in view except to enlarge their 

 knowledge of living things. The title of the book has not been 

 so strictly interpreted as to exclude a few insects which are 

 neither injurious nor useful, but either very plentiful or par- 

 ticularly instructive. 



In my own teaching of economic entomology and other 

 branches of biology, the laboratory work always comes first, and 

 the class-work is only a means of correcting and driving home 

 the instruction of the laboratory. Common insects are pro- 

 vided in large quantities, so that every student is supplied. 

 The rarer ones are exhibited in glazed cases, each of which 

 illustrates a single life-history. The teacher should make 

 his own selection of types, and draw up his own syllabus 

 of work, referring to the text-book wherever a detailed account 

 is required. It is good to draw much from nature, and to 



