ORTHOPTERA— ACRLDIDAE— INTRODUCTORY REMARKS. 853 



Although the author, in his diagnoses of these groups, reveals the fact 

 that the distinctions in one case are greater than those in another, yet so 

 far as the arrangement and naming is concerned they stand as equivalents. 

 No one will contend for a moment that the difference between Acrid/ urn 

 and GUdipoda is as great as between either of these and Proscopia or Tettix. 

 Yet Dr. Stal's system does not indicate this fact, as his groups stand as 

 equivalents. 



If we compare the true Acridians, as Acridium, (Edipoda, &c, with the 

 Tettigi, we find the following differences : — 



Aceidii. — Of various sizes, from half an inch to four inches in length ; 

 wholly terrestrial in their habits. 



Tarsi furnished with a pulvillus, or pad, between the claws ; although 

 sometimes minute, yet it is seldom, if ever, absent. 



Pronotum consisting of a kind of shield, covering the prothorax and 

 extending backward at farthest only upon the base of the elytra. 



Prostemum drawn up ; that is, it is not in the same plane as the rest of 

 the sternum ; spined, tuberculate or smooth, but never advanced upon the 

 mouth. 



Mouth, free, not covered by the presternum. 



Elytra and wings generally present, but sometimes aborted or entirely 

 wanting ; but, when present, the latter never exceed the former in length. 



But an examination of the Tettigi reveals an entirely different set of 

 characters in all these respects, as may be seen from the following statement 

 of them : — 



Tettigi. — Generally of small size, many being less than half an inch in 

 length, and seldom exceeding an inch, preferring moist damp situations, and 

 in some cases even subaquatic. 



Pronotum forming a shield over the entire bodv, extending 1 backward 

 nearly or quite to, and often beyond, the tip of the abdomen ; sometimes 

 flat, sometimes keeled and arched, and in some species elevated into a sharp 

 foliaceous crest. 



Tarsi without pulvilli, or pads, between the claws. 



Prostemum depressed to the same plane as the rest of the sternum ; 

 advanced upon the mouth, and usually furnished with a kind of semicircu- 



