PART II. 

 THE INSECT WORLD. 



CHAPTER I. 



GENERAL CLASSIFICATION. 



Those structures which are of economic importance and, in- 

 cidentally, those that are used in classification have been described 

 in the first part. 



Classification is the arrangement of the insects into series 

 which are so related to each other that a species never before 

 seen may be recognized, and its place ascertained from certain, 

 easily discernible, structural characters. 



Insects that agree in structure usually have similar habits, and 

 by placing an example into its systematic position, the probable 

 life cycle becomes also known, and its exact life cycle can be 

 more easily and intelligently traced out. 



The divisions used are orders, fimilies, genera, and species. 

 The term sub- may be prefixed to either, to indicate a division 

 not marked enough to claim full rank. 



A species consists of individuals which agree with each other 

 in appearance, structure, and life history, mating freely, produc- 

 ing progency, which resemble the parents, and which are them- 

 selves fertile. An assemblage of such species agreeing in general 

 characters forms a genus, and this is a more or less uncertain 

 division, depending somewhat upon the opinion of the systematic 

 student. A series of genera agreeing in form, structure, and 

 life history makes a family, and families are united into orders. 



For the division into orders, use is made of wings and mouth 

 structures and of the transformations. 



For convenience in ready classification the Linnaean orders are 

 here adopted, though some of them have been properly sub- 

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