1918] 



Thoracic Sclerites of Dissosteira 



349 



(in which the letters "x" are contained in Text figure 2). 

 Whether the angle containing the two letters "x" (Text figure 

 2) is a right angle, or an acute angle, is a feature used in classi- 

 fication. If the sides of the posterior region of the pronotum 

 instead of making an angle, extend approximately straight 

 across, the pronotum is spoken of as truncate posteriorly. Sim- 

 ilarly, if the anterior margin is approximately straight, it is 

 spoken of as truncate anteriorly. Whether the surface of the 

 pronotum is smooth, granulated (powdery appearing), wrinkled, 

 rugose or roughened with numerous tubercles, are other features 

 of value in classification. 



Fig. 1. Ventral view of prosternum of i?Aowa/ga. 



Fig. 2. Dorsal view of upper portion of pronotum of Dissosteira. 



Fig. 3. Vertical transverse section through wall of pronotum of Dissosteira. 



In the grasshopper Dissosteira, the pronotum is divided by 

 a notch "n" (Fig. 1) and an impressed line "su" extending 

 downward from it, into a front and hind lobe. The dorsal 

 ridge "mc" (Fig. 1 and Text Figs. 1 and 2) extending longitu- 

 dinally along the median line of the pronotum is called the 

 median carina, and in Dissosteira it is broken by a single notch 

 "n" (Fig. 1), while in other grasshoppers there may be two 

 such notches. The median carina "mc" of Fig. 1 is high and 

 arched on the hind lobe of the pronotum of Dissosteira, but in 

 other grasshoppers it may be nearly obsolete on the hind lobe. 

 This, and other features, such as whether the median carina is 

 irregular (as in Dissosteria) or whether it is even in contour, are 

 features used in classification. 



