184 WM. REES B. ROBERTSON 



16), pronotum not extended over the abdomen (figs. 7, 8, 14-16, 

 msHhx.), and elytra are present and elongated (figs. 7, 8, 14-16, 

 ely.) except in cases of brachypterism. It is easy to see the much 

 closer resemblance in all these characters among the subfamilies 

 represented in figures 7, 8, and 15 than between any of these 

 and the Tettigidae. Thus, on the basis of these body characters 

 the Tettigidae are clearly marked off from the Acrididae. 



Internal structures present equally distinguishable characters. 

 No organs illustrate this better than the gastric caeca. In the 

 Acrididae the five caeca (fig. 18) have each a large anterior 

 and a smaller posterior extension (pouch). The crop (fig. 18, 

 iglv.) is relatively larger and more rectangular anteriorly than 

 in the Tettigidae (fig. 17). In the latter the caeca have only an 

 anterior prolongation. There are, however, two circular ridges, 

 which may possibly serve for posterior caecal pouches. 



In the reproductive organs also are characters distinguish- 

 ing the two groups. In the usual acrididean testis the folli- 

 cles are long, sac-like structures joining the vas deferens close 

 together (fig. 22). This gives the testis a tassel-hke appearance. 

 Figure 22 is of Dissosteira Carolina, an oedopodine, and is 

 representative also of the Truxalinae and Acridiinae. In the 

 Tettigidae the plan of structure is more primitive. The fol- 

 licles are connected with the vas deferens at considerable dis- 

 tances apart in regular order (fig. 21), as in the typical acrididean 

 ovary, except that ov^rioles are not nearly so numerous as 

 testicular follicles. 



In histological characters there are also the same two types. 

 The appearance of the tettigidean testicular folhcle in longi- 

 tudinal section (fig. 19) differs much from that of the Acrididae 

 (fig. 20). It may even be said to look more like that of Gryl- 

 lidae or Locustidae. The cell cysts extend completely across 

 the folhcle (fig. 19). This is not true of the Acrididae (fig. 20), 

 but is true of Gryllidae and Locustidae. The cytoplasm of 

 spermatogonia! and spermatocyte cells is more compact, and 

 the meshes of the cytoplasmic network are much smaller than 

 in the Acrididae. This is also a gryllid character. These facts 



