22 INSECTS IN GENERAL. 



whole sentence in English. It is also an important consideration that 

 in learning- the elements of any science or art, an indispensable part of 

 such education is to acquire a knowledge of the more common techni- 

 cal terms which pro])erly belong to it, and which constitute its peculiar 

 plirascology, and which the student will continually meet with in all 

 writings upon the subject. In a work intended, like the present, for 

 the common student, all unnecessary use of such words should, of 

 course, be avoided, and whenever we have found it necessary to use 

 them, we have taken care, as a general lule, to explain their meaning, 

 either directly or by the nature of the context. 



The student must not expect that any science can be so simi)lified as 

 to remove all difliculties ; and especially true is this of so extensive and 

 complex a science as entomology. Nor is it desirable that this should 

 be done. One of the i)rincii>al advantages to be ex[)ected from the 

 stu<ly of this science is the admirable mental discipline which it aUbrds. 

 The forms with which it has to deal are so numerous and diversified, 

 and often, at the same time, so ck)se]y allied, that their classification 

 conslaiitly denumds a mimite and careful examination, and a discrimi- 

 native analysis, which, regarded purely as an exercise of the mind, are 

 scarcely inferior to those re<piired by the al)stract mathenuitics, whilst 

 they i>ossess the additional interest which naturally atttiches to the 

 study of living beings. 



CLASSIFICATION AND NOMENCLATURE. 



Classification in natural history has two objects in view — first, to 

 show the relationship which exists between organized beings, by put- 

 ting them in groups in accordance with the similarity of their charad- 

 ters; and secondly, to facilitate the study of them by enabling the stu- 

 dent to co]ni)rehend a great number of dilferent but allied forms under 

 a comparatively small number of general heads, and thus to afford an 

 important aid to the memory. 



liy nomenclature is meant the gi\'iug to these groui)s an«l the species 

 which compose them distinctive names. This is necessary to enable us 

 either to receive or to communicate knowledge ; and without it natural 

 history could not be raised to the dignity of a science. 



In a department so extensive as that of insects a very great number 

 of names, not only of species, but of the grouiis in which these are 

 comifrehended, must be necessarily introduced. It is therefore import- 

 ant that the science shall not be encumbered by the creation of unneces- 

 sary genera, or such as are founded upon slight and unimportant char- 

 acters. It is, indeed, often difiicult to determine precisely what charac- 

 ters or combination of characters necessitate or justify the formation 

 of a new genus, or the subdivision of an old one. No definition of the 

 term geiius which is universally applicable ever* has been, or perhaps 



