GEOLOGICAL SUEVEY OF THE TEEEITOEIES. 433 



than tlie AcrkUdcG. Not only does Acrididce contain nearly twice as 

 many species as Locttstidcej bnt the number of individuals of the former 

 is, if we omit the single species Anabrus simplex, infinitely greater than 

 the latter. 



In Mr. Scudder's Materials for a Monograph, he mentions 41 species 

 of Lociistidce, and but 38 of Acrididce, exclusive of Tettigince ; Serville, 

 in his Hist. Kat. Orthopteres, describes 142 species of the former, and 

 172 of the lattery and Walker, (Cat. Dermap. Salt. Orthop.,) exclusive 

 of the TetUgince and additions in Part Y, enumerates 9L0 species of the 

 former and 921 of the latter. These show that, as a rule, the two fam- 

 ilies contain nearly the same number of species. But, while this appears 

 to be the general rule, in the West there are 60 species of Acrididce to 31 

 of Locustidce. 



Although the number of individuals of one of the species of Acridini 

 is far in excess of the number of individuals of any species of CEdipodini, 

 yet a glance at the tables will show that the number of species belong- 

 ing to the latter group is much larger than that of the former, (Edipodct 

 alone containing 21 species. And while in the eastern and middle dis- 

 tricts Caloptemis spretus only is migratory, when we cross into the west- 

 ern district (Edipoda atrox is the destructive migratory species, indicat- 

 ing an approach to the oriental orthopteral characteristic. 



An examination into the different species of the Locustidce brings out 

 another important fact corresponding with the nature of the regions 

 under consideration. Out of 31 species 23 are either wingless or have 

 these organs so aborted that they are unfit for flight, indicating most 

 clearly the absence of arborescent vegetation, and the prevalence of ex- 

 tensive treeless plains. The number of Geutliopliili is larger than I had 

 expected to find it, as, upon the theory I have adopted, these affect 

 damx) })laces, and are confined more to the margins of water-courses, 

 lakes, &c. ; but the fact that the species are confined to the eastern and 

 western districts somewhat conforms to this idea. 



III.— A LIST WITH DESCEIPTIOKS OF NEW SPECIES. 

 Family L— GRYLLIDiE. 



Gryllus aVorematus, Serv. 



Found throughout Colorado, in Wyoming, and occasionally in North- 

 ern Utah and Southern Idaho. SpeciDiens generally large, the length 

 of the ovipositor exceeding the measurements given by Mr. Scudder. 



G. luctuosus, Serv. 



I met with this species in the extreme northern part of Utah, and in 

 Southern Idaho, where it appears to rex)lace the former species. Size 

 larger than the usual measurements, and ovipositor longer, yet I feel no 

 doubt that the specimens referred to this species belong to it. Plate 

 I, Figures 10 and 11. 



OecantJms niveus, Serv. 



I am not positively certain that my specimens belong to this species, 

 as most of them are more or less injured. It occurs in considerable 

 numbers along the banks of streams lined w.ith bushes. 



TridactyUis, .(?) 



I saw what I am quite confident was a specimen of this genus on the 

 bank of Bear Ivivcr in Cache Valley, Utah, but was unable to capture 



28 a s 



