EXTERNAL ANATOMY. 



Fisr. 31. — lyateral view of the thorax 

 (pleiirites) of Melanoplus bivittntus. 

 Original. 



half of the metasternum are the lower ends of the meta- 

 thoracic episterna {meta. epis), separating the fossae of the 

 second legs from those of the third and sending prolonga- 

 tions backwards to form the inner margins of the latter. 



In a side view of a 

 thorax, (Fig. 31), from 

 which the pronotum, wings 

 and legs have been re- 

 moved, the space above the 

 leg foss£e is occupied by 

 four rectangular pieces, 

 which slope obliquely up- 

 wards and forwards. The 

 anterior margin of each of 

 these is marked by a dark 

 stripe or band of pigment, 

 and the posterior margin 

 by a light stripe. The first or most anterior piece is the 

 mesothoracic episternum{meso.epis) . Its lower margin is pro- 

 longed downwards and backw^ards and forms the anterior 

 and lower boundary of the fosscC of the second leg. The 

 second piece is the mesothoracic epimeron, {meso. em). Its 

 lower end forms the upper and posterior margin of the leg 

 fossae. The third piece is the metathoracic episternum. 

 [meta. epis). The fourth \st\\e metathoracic epimeron [meta. 

 em). Between the metathoracic epimeron and metathoracic 

 episternum, just above the mesothoracic leg fossae, is a 

 small oval aperture provided with a pair of lip-like chitin- 

 ous valves. This is the respiratory aperture or spiracle, 

 (sp) of the metathoracic segment. Along the upper margins 

 of the episterna and epimera are a few small, irregular 

 pieces, to which the wings are articulated. The dorsal sur- 

 face of the meso-and metathorax, (Fig. 32), is formed by 

 two nearly square areas, which occupy the space betw^een 

 the wings. The\^ are soft and membranous, and the pieces 

 which compose them are not sharply defined. The anterior 



