xii INTRODUCTORY. 



battery of insecticides, the philosophy of their application will 

 remain the same. To do this it is necessary to give an outline 

 of the characteristics of insects generally ; of those features that 

 distinguish them from all other animals, and of those peculiarities 

 upon which we must base our hope of conquering them. Enough 

 of the structure is described to show how they are built up, and 

 all the different orders are referred to, so that the intelligent 

 reader may recognize at least the group to which a specimen 

 belongs and may be able to determine whether or not an injurious 

 species is in hand. The direct needs of the agriculturist have 

 been kept constantly in mind ; but the effort has been to give 

 also a general information on tlie subject of insect life, and the 

 work should be useful to students in all save advanced college 

 courses, where technical or svstematic studies outrank all others. 



