THE VARIATION AND CORRELATIONS OF 



there the taxonomist's work is easy. Where there are no sharp breaks, 

 but evolution has proceeded by simply enlarging here and diminishing 

 there, the taxonomist must pick out stages which seem to be important 

 for one reason or another and give them names by which others will 

 recognize what is being talked about. These "species" may not have 

 the distinctness that has been postulated for things of specific rank,* 

 but they are necessary, and they are, as far as we know, the next 

 rank below "genus. " We must have shorthand expressions for describ- 

 ing our specimens. I, personally, would prefer a formula such as Teg. 

 12, P. F. 10, Ovip. 16, but the taxonomic world would probably deny 

 me that privilege; and so, where necessary, the names in common usage 

 must be used and for the sake of convenience we need more of them. 

 However, since I feel that in Gryllus these names mean nothing more 

 than rough descriptions of dimensions, and since from the nature of 

 this paper the dimensions are given in detail, I have largely abstained 

 from the use of specific names. 



2. COMPARISON OF THE LONG-WINGED AND SHORT-WINGED GROUPS. 



In considering the relations between the long-winged and the short- 

 winged groups we should bear clearly in mind the nature of the dimorph- 

 ism. Brues (1903), writing of insects having vestigial wings, offers 

 the following categories into which he believes it possible to class all 

 such cases: 



(1) Wings having essentially a pupal character, i. e., developing as 

 normal wings up to the pupal stage but failing to expand. 



(2) Wings essentially normal, except for their smaller size and less 

 complex venation; sometimes even developing a color pattern, or pos- 

 sessing unique and quite distinctive characters. 



(3) Wings consisting of little more than a hollow bag and giving no 

 clue from their appearance as to the probable wing-structure of their 

 ancestors. (Comparable in a way to the halteres of the Diptera. ) 



Class 1 is a very common type among the rather near relatives of 

 Gryllus. Whole genera of the Locustidas, e. g., Ceuthophilus, never 

 develop wings beyond the pupal state. Myrmecophila, of the Gryllida?, 

 also comes in this category. But all the species of Gryllus, as far as I 

 know them, pass beyond this stage and develop imaginal wings of some 

 sort. The short wings of Gryllus fit most nearly Brues's class 2. The 

 short wings are essentially normal in all respects, except for their 



*Sharp (1882) puts this postulate very concisely. He says: 



"I believe, if we limit our view to the creatures coexisting t the present moment, 

 no naturalist could be found who would venture to deny the existence of species 

 as real and objective. It is, in fact, perfectly clear that the hosts of individuals 

 living around us are arranged in clusters or groups, isolated from other clusters or 

 groups; .... no practical naturalist will be found who will deny the reality of 

 the existence and isolation of such clusters, and it is these we call species." 



