102 



ORTHOPTEROUS GROUP INSARAE 



of the tegmina in both sexes and the stridulating field in the male 

 are of the greatest diagnostic importance. The tendency toward 

 brachypterism in the females of this genus is apparently speciali- 

 zation, correlated in its extreme condition (in group C) with the 

 highest development of the male sound-producing apparatus. 

 Two other of the four species-groups show pronounced brachypter- 

 ous tendencies, the forms exhibiting the same {arachnopijga in group 

 A and semialata in group B) being divergent from the main phyla of 

 these groups and apparently the most specialized of each. In 

 gracilipes constricta we find tendencies toward brachypterism de- 

 veloping within the race, the normal condition of which is as truly 

 macropterous as is true gracilipes. In the male tegmina the rela- 

 tive proportions of the stridulating field, its length compared with 

 that of the pronotal disk, the production of the apical section of 

 the stridulating vein, the form of the margin and of the speculum 

 are the chief characters of importance. The genitalia, which are 

 discussed below in more detail, are of diagnostic importance in a 

 few of the species, but in one case (the plastic gracilipes) the male 

 cerci might be called polymorphic. 



The following diagram illustrates our ideas regarding the group 

 relationship of the species. 



arachnopyga 



c 



gracilipes 



gracilipes constricta 



■insaroides 



phalangium 



grallator 



semialata 



car it a 



brevicauda 



limifcra 



I) 



■ phantasma 



