Evolution and Taxonomy 51 



Although, doubtless, the great extent to which the wings 

 are still used in taxonomy is partially due to the ease with 

 which wing characters can be observ^ed, still the following 

 considerations show that such use is warranted by the facts of 

 nature. 



The chief end of existence of an adult insect is to provide^ 

 for the perpetuation of the species. This resolves itself in tho.- 

 case of the male into seeking a mate ; and in the case of the. 

 female after accepting a mate, into seeking a proper nidus for 

 her eggs. In the case of certain insects special conditions ne- 

 cessitate a prolonged existence in the adult state in order to 

 accomplish this end in the best manner ; in such cases there 

 may exist a necessity for .seeking food ; but in many families 

 all nourishment is taken during the adolescent stages. 



The necessity for seeking mates or for properly placing 

 eggs, as well as for seeking food gives great importance to 

 organs which increase the power of locomotion. It follows 

 from this that when organs of flight had once been developed 

 such organs would furnish an important field for; the action 

 of natural selection. 



It has been indicated that there is good reason to believe 

 that all winged insects have descended from a. common 

 winged ancestor. But we find that the primitive type of 

 wing has been modified in many widely different ways. 

 Hence a study of the various ways in which, wings have been 

 specialized can not fail to throw much ligh.t on the. phylogeny 

 of insects. 



The fact that in some cases, notably those of most animal 

 parasites, wings, becoming unnecessary and perhaps even 

 detrimental, have been lost does not lessen the value of. these 

 organs for taxonomic purposes when they have b^en pre- 

 served. 



It is often urged, that as the wings are merely appendages 

 of the body, they are extremely liable to be modified in form ; 

 and that consequently we cannot hope to find in them a very 

 permanent record. In other words, while it is generally ad- 

 mitted that variations in the framework of the wings may give 

 us important clews as to the limits of the genera, we can not 



