84 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 82 



extends through the tarsus and tibia into the femur. In Dissosteira 

 two small groups of fibers of the claw muscle arise in the upper part 

 of the tibia (fig. 39, isph, 139c), and one arises posteriorly in the 

 base of the femur (fig. 36 A, 78). The pull of the muscles on the 

 tendon retracts the unguitractor plate and flexes the claws ventrally. 

 The extension of the claws probably results from the elasticity of 

 their basal connections and the pressure on the supporting surface. 

 Typically, the muscles of the pretarsus should arise in the tarsus. 

 It is probable, therefore, that the extension of the fibers into the tibia 

 and femur in insects (and also in chilopods and diplopods) is a sec- 

 ondary condition produced by a proximal migration of the primitive 

 muscle. In Crustacea and Arachnida the pretarsus, or dactylopodite, 

 is provided with levator and depressor muscles, both of which have 

 their origin in the tarsus, or propodite. In some Arachnida there are 

 two pretarsal claws, as in most insects, but the pretarsus has lateral 

 articulations with the end of the tarsus, and is provided with dorsal 

 and ventral muscles. 



V. THE WINGS AND THEIR MECHANISM 



The wing mechanism of the grasshopper is equally developed in 

 each segment of the pterothorax. The hind wings, though much more 

 extensive than the forewings, or tegmina, and probably the chief 

 organs of flight, have no advantage over the latter except in the 

 stronger development of the flexor apparatus. The forewings, on the 

 other hand, have a more powerful levator equipment than the hind 

 wings because of the presence in the mesothorax of the second pair 

 of tergo-stemal muscles attached dorsally on the scutum (fig. 34, 84). 

 In structure, the hind wings (fig. 45 B) dififer from the forewings 

 (A) only in the reduction of the costal area and in the great ex- 

 pansion of the anal area. 



STRUCTURE OF THE WINGS 



In general structure, articulation, and mechanism the acridid wings 

 dififer little from the wings of other Orthoptera. The tegmina when 

 at rest are flexed over the body in a manner to form a high roof with 

 steeply sloping sides (fig. 50 A, W2) covering the back of the abdomen 

 and inclosing the folded hind wings {Wo) in the space above the 

 latter. The anal areas of the tegmina overlap dorsally in a median 

 horizontal plane, the left tegmen being usually on top ; the pre-anal 

 areas form the lateral inclines of the tegminal roof. The bend be- 



I 



