390 DIMORPHISM IN FEMALES OF AUSTRALIAN AGRIONID^. 



of the insects, particularly the build of the head and thorax, and 

 the relative proportion of expanse of wing to total length (about 

 5 to 4 in both genera). So great is this similarity that, if the 

 wings were removed from one of the "orange" females of 

 Agriocnemis priiinesceiis, one would unhesitatingly declare it to 

 be a new form of the female of /. heterosticta or an allied species; 

 and such I took it to be until I saw the difference in the neura- 

 tion of the wings. That the same cause has brought about dimor- 

 phism in both genera is scarcely open to doubt; and it is probable 

 that the dimorphism is in some way connected with the preserva- 

 tion of the species. 



