CHARACTERS OF MIGRATORY LOCUSTS. 35 



A A, Head more or less ovoid or siibglobular; face perpendicular or 

 nearly so, never very oblique, tbough often somewhat arcuate 

 below; antennae filiform, subdepressed or clavate, and not en- 

 larged at the base; hind legs generally robust and very distinctly 

 enlarged at the base. 

 a. Prosternum or front breast armed with a spine or tubercle. 



Acridhii, 



a a. Presternum unarmed , Ocdipodini. 



Although at least one species of Oedipodmi is migratory in the Old 

 World, and a species in North America (Gamnula pelliicida Scudd.) be- 

 longing to the same group was formerly supposed to be the migratory 

 locust of California, yet at present our observations are confined to 

 Acridini, which contains the destructive locust of the West. This limits 

 us to those species found in the United States which have the head more 

 or lees subglobular or ovoid, and the front breast armed with a spine. 

 The latter character is easily recognized by any one, as the spine may 

 be seen by examining the under side of the neck ; it usually stands out 

 like a little blunt thorn, very distinct. If this is wanting, the observer 

 may know without further observation that his specimen does not belong 

 to the migratory species of our country. If it has the spine, and the 

 head is not conical or pyramidal, then he must refer to the characters 

 hereafter given of the genera and species. 



We have now reached the genera, which cannot be fully discussed at 

 present, as this w^ould require, if properly done, a revision of the Calop- 

 teni and Pezotettigi, and an examination of all our native species. We 

 will, therefore, simply mention the more important genera of the group 

 represented in the United States, calling attention to a few of the more 

 XDrominent characters by which Caloptenus is separated from those genera 

 most closely allied to it. We will also make use of localities, habits, &e., 

 wherever they will assist the general reader in any way in determining 

 whether or not a given specimen belongs to Caloptenus. 



The following genera of Acridii which are mentioned by North Ameri- 

 can authors may be omitted from further consideration for the reasons 

 given below : 



Tropidacris, DictyopJiorus, EJiomalea, Ommatolampis^ Platyphyma^ 

 Dactylotum^ and Chrumacris, 



The first contains only gigantic species, and if represented at all in 

 the United States, it is only by a single species occasionally found along 

 the southwestern border of Texas. 



Rhomalea may be considered as a synonym of DictyapJioriis, which is 

 represented by but two subtropical species, which are large, with 

 brightly colored under-wings, chiefly red ; while those of our Calopteni 

 are transparent. 



Ommatolampis has been superseded by Mr. Scudder's new genus Kcs- 

 perotettix. 



