NO. 2 THORACIC MECHANISM OF A GRASSHOPPER — SNODGRASS 



77 



muscles (fig. 44). The ventral, flexor muscles are inserted upon an 

 apodeme that arises from a small sclerite in the ventral membrane of 

 the knee joint. The knee mechanism is most strongly developed in the 

 hind leg (figs. 36 F, 39) . The base of the tibia here forms a well dif- 

 ferentiated articular head bent toward the femur almost at right angles 



Fig. 42. — Tarsus and pretarsus of Dissosteira. 



A, tarsus of middle leg disjointed, showing levator and depressor muscles 

 (loS, log) inserted on basal subsegment, and tendon-like apodeme (iioAp) 

 of retractor of claws (Un) arising on unguitractor plate (Utr) and extending 

 through tarsus. 



B, dorsal view of distal end of tarsus (Tar), arolium {Ar), and claws (Un), 

 the latter articulated to unguifer (Uf) of tarsus. 



C, ventral view of pretarsus and end of tarsus, showing planta (Pin) and 

 unguitractor plate (Utr) in base of pretarsus. 



to the length of the segment (fig. 39), and the dorsal lip of the tibial 

 base is produced far into the end of the femur by an inflection of the 

 articular membrane. The first and second tibiae are each provided 

 with two rows of large, flexible, hollow spines on the distal half of 

 the under surface, while the hind tibia has two rows of similar spines 

 on its dorsal surface, but none on the ventral surface except at the end. 

 The tarsi. — The tarsi are each composed of three segment-like pieces 

 (fig. 40, Tar) ; but the tarsal subdivisions, or articles, are clearly not 



