34 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 82 



The neck skeleton of Dissosteira consists of two pairs of small 

 cervical sclcrites situated ventro-laterally in the membranous walls of 

 the neck (fig. 20 B, icv, 2cv). The two sclerites of each pair in the 

 grasshopper are closely hinged to each other, and form a bridge on 

 each side between the head and the prothorax. The first sclerite ( icv) 

 is an irregularly triangular plate articulating with the occipital con- 

 dyle (fig. 2)^, g) of the posterior rim of the head, situated just above 

 the base of the posterior tentorial arm (A, PT). Immediately behind 

 its articulation this plate bears externally two small lobes that are 

 conspicuous by their covering of short hairs. The second cervical 

 sclerite (fig. 20, B, 2cv) is a slender bar articulating posteriorly with 

 the anterior margin of the prothoracic episternum {Eps) just within 

 the overlapping edge of the protergum. The two cervical sclerites of 

 each pair are movably hinged to each other at an angle directed ven- 

 trally. They are mostly concealed when the head is in the usual re- 

 tracted position, but they form a small prominence of the neck pro- 

 jecting just behind the base of the maxilla. The probable function and 

 mechanism of the cei-vical sclerites will be described in connection with 

 the account of the muscles inserted upon them. 



The lateral, muscle-bearing cervical sclerites are probably homolo- 

 gous structures in all insects in which they occur. Dorsal and ventral 

 neck plates are presnt in some insects, but they are variable in size and 

 arrangement and are probably secondary sclerotizations of the neck 

 membrane. 



THE PROTHORAX 



The prothorax of the grasshopper is a highly individualized segment 

 of the body, for, though its posterior dorsal and lateral parts widely 

 overlap the anterior part of the mesothorax, it is separated from the 

 latter by an ample intersegmental membrane (fig. 20 B, Mh). 



The external parts of the prothorax comprise tergal, pleural, and 

 sternal sclerites. The principal plate is the tergum, a large bonnet-like 

 piece that covers the back and most of the sides of the segment (fig. 

 20 A, T). Only a corner of each pleuron shows externally: this is 

 the small triangular lobe lying anteriorly between the base of the leg 

 and the lower margin of the tergum (fig. 20 A, Eps). The rest of the 

 pleuron is deeply invaginated within the lateral wall of the tergum 

 (B, Eps). The prosternum consists of two sclerites in the ventral wall 

 of the segment between the bases of the first legs (fig. 21 A, S, Ss), 

 the anterior one connected by the precoxal bridges (Acv) with the 

 pleura. The prothoracic legs appear to be inserted between the ster- 

 num and the lower edges of the tergum, but the lateral connections of 



