34 REPORT UNITED STATES ENTOMOLOGICAL COMMISSION. 



tubercled, or smooth, but never advanced upon the mouth in the form 

 of a muffler; elytra or upper wings, when present, always as long as 

 the wings ; tarsi with pads between the claws. 



The third subfamily, Tettigince, is characterized by having the prono- 

 tum, in the form of a shield, extending backward nearly or quite to the 

 tip of the abdomen, and sometimes even beyond it; the prosternum in 

 the same plane as the rest of the sternum, and advanced upon the mouth 

 in the form of a mufder; elytra when present usually shorter than the 

 wings, and placed at the sides of the body ; tarsi without pads between 

 the claws. 



The two latter families are represented in the United States, but 

 the great body of our locusts belong to the Acridince, the species of 

 Tettigince being comparatively few, quite small, and seldom noticed by 

 unscientific observers. As the Caloptenus spretus and all other migra- 

 tory locusts belong to Acridince, we shall limit our further consideration 

 to this subfamily. It contains several subordinate groups, but the charac- 

 ters by which these are distinguished from each other are not so appar- 

 ent and uniform as those separating the subfamilies, nor is it necessary 

 for us in this general report to attempt an explanation of these differ- 

 ences. Perhaps we may as well state here thac no arrangement we have 

 seen can be considered satisfactory. The form of the head and antennae, 

 formerly selected as characters, are too indefinite to meet the demands 

 of science, while those adopted by Stal in his most recent arrangement 

 can scarcely be considered of sufficient value or importance to render 

 them more satisfactoi'y ; they also fail to separate forms which we think 

 ought not be brought together. To bring together the long conical head, 

 ensiform antennse, and elongate body of Truxalis with the round head, 

 filiform antennse, and massive bodies of some of the heavier Oedipodce, 

 and to separate such forms as Facliytylus migratorius and Acridium pere- 

 grimmi, cannot be justified simply because of the presence or absence of 

 a little prosternal spine or transverse pronotal sulcus. The difficulty 

 arises from the fact that the Truxalidce gradually separate into the two 

 branches represented in part by the Acridii and Oedijwdce, the transition 

 from the former to the two latter being so gradual that it is almost im- 

 possible to mark the dividing line. But any system which fails to recog- 

 nize the Truxalid group and yet separates the two latter is defective and 

 unsatisfactory. 



Therefore, for want of a better arrangement, we adopt for the present 

 the following, although aware that it is defective, but it enables us to 

 eliminate the Truxalid group, which is the only use we wish to make of 

 it at this time. 



A, The head conical or pyramidal; the face very oblique, or sloped 

 under toward the breast ; the antennse usually, though not 

 always, enlarged at the base ; hind legs comparatively slender. 



TnixalinL 



