Tnd'oduction to the Sj/nopsis of the Acrididce. 259 



ca^es (as in Mesops Boopeclon, some species of Opomala, etc.) the pro- 

 notum is cylindrical. The lateral carina? afford important generic and 

 specific distinctions, by their relation to each other, shape, etc., as to 

 whether they are parallel or convergent, straight or curved, cou- 

 tiniious or interrupted. The front margin of the jironotuni seldom 

 presents any angular points, being usually obtusely rounded or trui\- 

 cate ; but the posterior extremity generally extends backward, in a 

 rounded or angular form, upon the base of the elytra ; in a few cases 

 (as Chrysochraon, and some species of Pezotcttix, in which the elytr.a 

 and wings are wantmg) the posterior margin is truncate. The poi- 

 terior latercd margins are the hind margins running down from tlie 

 extremity of tlie dorsum to the posterior angle of the sides. 



The body of the pronotuin is generally divided into* four lobes bv 

 three transverse sutures or impressed lines ; the lobe, or portion next 

 the head, is the .anterior lohe, the hindmost one the posterior lobe, the 

 other two the middle lobes. In many species the two anterior im- 

 pressed lines are indistinct, or w-anting, but the posterior one is .nearly 

 always present, except in the Tdtigince. These lines are sometimes 

 designated by the numbers 1, 2, and 3, beginning with the front one 

 and counting backward. 



The general form of the pronotum affords verv important chai-ae- 

 ters : sometimes the width is uniform and the sides are j^arallei; 

 sometimes they diverge posteriorly ; at other times they apj)roach eaoii 

 other in the middle, in which case the pronotum is said to be constricted, 

 but this terra applies only when the narrowest point is between tlie 

 extremities. Its surface also varies : is smooth, punctured, rugose, or 

 tuberculate. 



The mesonotum and metanotum are hid by the pronotum and the 

 wings, and are not used in descriptions, except in the case of a few 

 wingless species of Pezotettix. 



The proaternum, or under side of the prothorax, is short, and is 

 either smooth, that is, it is without either tubercle or spine, or it is 

 furnished with an obtuse tubercle, or a conical spine, called the prvs- 

 ternal spine. The species furnished with this spine are said to have 

 the prosternum armed or mucromde (Opomala, Mesops Romalea, and all 

 the group of Acridini) ; when the prosternum is without a spine it is 

 smooth or unarmed (as Tryxalis, Pyrgoraorpha and the entire groupi.:, 

 (Edipodhii and TeUigini). This spine is either subcylindrical (;r 

 cuneiform, obtuse or acute, straight or curved, etc. : these differenc<.'s 

 furnishing either generic or specific characters. Those species without 

 the prosternal spine generally have the prosternum marked with a 

 transverse curved groove, more or less distinct. 



