78 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 82 



segments equivalent to the other parts of the leg, for they are inter- 

 connected only by infolded membranes in which there are no sclerotic 

 points of articulation, and none, except the basal one, is ever provided 

 with muscles (fig. 42 A). The large basal subsegment of the grass- 

 hopper's tarsus bears three pairs of cushion-like pads on its under sur- 

 face ; the middle subsegment has a single pair ; the longer terminal one 

 has no pads. The presence of three pads on the basal subsegment is 

 suggestive that this piece is a composite of three primary tarsal articles. 

 The tarsal pads have been termed euplantidae by Crampton (1923). 

 The pretarsi. — The terminal segment in each leg of the grasshopper 

 bears a pair of large lateral clozi's (fig. 42 A, Un), but it is itself 

 reduced to a simple median lobe, the arolium (B, C, Ar), and has two 

 sclerites in its ventral wall (C, Pin, Utr). The proximal sclerite is the 

 unguitractor plate {Utr) ; its base is invaginated into the end of the 

 tarsus and gives attachment to the tendon-like apodeme (iioAp) of 

 the depressor muscle of the pretarsus, known as the retractor of the 

 claws. A levator of the pretarsus is lacking in all insects. The distal 

 ventral sclerite, possibly a subdivision of the unguitractor, is distin- 

 guished as the planta (Pin). The claws arise from the dorso-lateral 

 parts of the base of the pretarsus and are articulated dorsally to the 

 unguifer area on the end of the tarsus (fig. 42 B, Uf). 



MUSCLES OF THE LEGS 



The muscles of an insect's leg are comprised in three groups: (i) 

 muscles that move the limb as a whole; (2) muscles that move the 

 telopodite ; (3) muscles that move the segments of the telopodite upon 

 each other. The muscles of the first group have their origins entirely 

 within the body ; they are inserted on the base of the coxa, on the tro- 

 chantin, or on apodemes arising in the coxal corium. The muscles of 

 the telopodite arise in the coxa and within the body ; they are inserted 

 on the trochanter or on apodemes arising close to the base of the tro- 

 chanter in the articular membrane of the coxo-trochanteral joint. The 

 muscles of the individual segments of the telopodite beyond the tro- 

 chanter arise in the segments proximal to their insertions ; they are 

 inserted either on the bases of the segments they move or on apodemes 

 arising in the articular membranes. 



Muscles of the leg base. — The muscles associated with the coxa that 

 move the leg as a whole fall into three groups according to their points 

 of origin ; namely, muscles that arise on the tergum, muscles that arise 

 on the sternum, and muscles that arise on the pleuron. 



