NO. 2 HONEY BEE — SNODGRASS 73 



The trochanter of each hind leg has two large levator muscles 

 (fig. 24 C, D, loj, 108), a long thoracic depressor (C, E, lop) arising 

 on the metathoracic arm of the endosternum (A, lop), and a single, 

 broad coxal depressor (C, E, no). The levators (lO/', 108) are 

 inserted in the dorsal articular membrane (D), the depressors (lop, 

 no) on a long ventral apodeme (Ap). 



The trochantero-femoral joint. — The hinge between the trochanter 

 and the femur differs from all the other leg joints in that its axis 

 traverses the vertical plane of the leg, and is, moreover, strongly- 

 oblique, the dorsal end being distal to the ventral end (figs. 13 H, 

 24 C). The movements of the femur on the trochanter, therefore, are 

 those of production and reduction, but, owing to the obliquity of the 

 hinge, the femur acquires also an upward slant as it turns backward. 

 A single reductor muscle activates the femur. 



The obHquity of the trochantero-femoral joint in the vertical plane 

 of the leg gives the trochanter a firm pressure or hold on the femur in 

 responding to the depressor and levator action of the trochanteral 

 muscles, the trochanter and the femur being thus moved as a unit on 

 the coxo-trochanteral articulation. 



The character of the trochantero-femoral joint differs but little in 

 the three legs of the bee. In each leg there is anteriorly a narrow 

 hinge line between the two adjoining segments (figs. 13 H, 24 C), 

 with an articular point {h) at the upper end; only in the hind leg is 

 there a definite ventral articulation (fig. 24 C, F, i). Posteriorly the 

 trochanter and femur are separated by a wide, thick, strongly elastic 

 conjunctiva (fig. 13 B, cnj). The femoral reductor muscle (fig. 13 H, 

 dj; fig. 22 D, G, 8g; fig. 24 C, ///) arises anteriorly by a broad 

 base in the trochanter and its convergent fibers are inserted on a 

 shelf like apodemal plate projecting from the posterior rim of the basal 

 foramen of the femur (figs. 13 F, 24 F, Ap). The contraction of 

 the muscle, therefore, turns the femur posteriorly on the anterior 

 hinge with the trochanter ; the muscle is opposed by the resistence of 

 the elastic posterior conjunctiva, which restores the femur to its 

 original position on relaxation of the reductor muscle. 



The femoro-tihial joint. — The "knee" joint of each leg has strictly 

 a hinge motion on a horizontal axis between anterior and posterior 

 articulations. The movements of the tibia, therefore, are those of 

 extension and flexion on the end of the femur; they are produced 

 by dorsal and ventral muscles lying in the femur. The head of the 

 tibia is somewhat bent toward the femur, and the hard wall of the' 

 femur is deeply emarginate below the joint, allowing the tibia to be 

 flexed close against the femur. 



