2 SxMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 94 



The primary object of the work here presented has been to arrive 

 at an understanding of the mechanisms of copulation and oviposition 

 in the Acrididae, which in this family present many peculiar features. 

 Neither of these processes, the writer believes, has been fully under- 

 stood or correctly described, though careful observations have been 

 made on the processes of copulation and egg-laying among grass- 

 hoppers. With the closer studies on the behavior of insects now found 

 necessary for economic purposes, it is becoming obvious that we must 

 understand more fully the structure and mechanics of the anatomical 

 mechanisms on which depends so much of the insect's activities. In 

 addition to the functional phase of morphology, however, there is the 

 no less important taxonomic aspect. Hence, in the following pages 

 much attention is given to structures bearing on the relationships be- 

 tween the Acrididae, Tetrigidae, and Tridactylidae. and a brief com- 

 parative study of the anatomy of the external male genitalia is included, 

 since these structures will undoubtedly be found to contain many 

 characters of importance for the separation of species where other 

 features are not sufficient for exact determinations. 



The writer follows Blatchley (1920), Walker (1922), Brues and 

 Melander (1932), and others in regarding the grouse locusts as 

 constituting a family (Tetrigidae, or Acrydidae) distinct from that 

 of the typical grasshoppers (Acrididae). Aside from superficial differ- 

 ences in such characters as the length of the pronotum, and in certain 

 features of the tarsi, the grouse locusts are distinguished from the 

 grasshoppers by the lack of the characteristic tympanal organs of the 

 latter, and in the totally different nature of the external male geni- 

 talia, which in the grasshoppers have a unique and highly standardized 

 type of structure that distinguishes the Acrididae from all other 

 Orthoptera. The tetrigids, of course, in many ways, particularly in 

 the general structure of the abdomen and in the structure and mecha- 

 nism of the female ovipositor, show their relationship with the Acridi- 

 dae, but this relationship is much more distant than is that of the 

 several acridid subfamilies with one another. Some orthopterists, 

 furthermore, would link the Tridactylidae with the Tetrigidae and 

 Acrididae, but to the writer a close association of the tridactylids with 

 the acridoid families seems doubtful, notwithstanding the close simi- 

 larity of the ovipositor in these two groups. 



I. GENERAL STRUCTURE OF THE ABDOMEN 

 The morphology of the adult insect abdomen is difficult to under- 

 stand because of the complete suppression of the segmental appendages 

 in the pregenital region, and the probable union of the appendage bases 



