134 AnyiaJs Entomological Society of America [Vol. IX, 



the variations arose, first, because the animals were subjected to 

 a new environment and the necessary modifications in the 

 behaviour caused modifications in structure, or that variations 

 in structure arose by orthogenesis and the animals were called 

 upon to find a suitable environment or perish. The latter 

 assumption seems to be the most reasonable. The agreement 

 between the two figures also suggests that the more fundamental 

 modifications in structure and in behaviour have been fairly 

 constant since their origin. 



SUMMARY. 



1. Movements preliminary to copulation are fairly constant 

 for each group of the Orthoptera and vary from very simple 

 (Mantidae, Phasmidce and Acrididee) to complex (Blattidas, 

 Gryllid^ and Locustidse). 



2. There is a sex discrimination in the males of all forms. 

 The female plays an aggressive part and displays a discrimina- 

 tion of sex in some groups while in others she is absolutely 

 passive. 



3. There is a typical mode of copulation for each family of 

 the Orthoptera. In the Mantidae, the Phasmidae and the 

 Acrididas there is a superposition of the body of the male. In 

 the Blattidas and the Gryllidae there is a superposition of the 

 body of the female. In the Locustidae there is an "end to end" 

 copulation. 



4. Families represented by the least number of subfamihes- 

 are highly specialized while those represented by the largest 

 number of subfamilies have a generalized type of reproductive 

 behaviour. 



5. A comparison between a classification based upon the 

 reproductive behaviour and one based upon paeleontological 

 evidence shows a striking agreement and suggests that the 

 different types of reproductive behaviour have been fairly 

 constant since their origin. 



