90 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 8o 



branches. The coxal branch (Q) spreads out in a broad fan on the 

 ventral wall of the coxa; the thoracic branch (fig. 39, P) includes 

 one or two long muscles from the tergum, one from the arm of the 

 pleural ridge, and sometimes one from the episternum (fig. 26 B, P), 

 the fibers from all sources converging upon a large apodeme that 

 arises from the ventral lip of the trochanter or from the articular 

 membrane close to it. The great size of the depressor muscles of the 

 trochanter gives the leg a strong movement of extension, which is 

 that by which it accomplishes its principal work. The ample mem- 

 brane above the trochanteral articulation allows the trochanter and 

 femur to be freely flexed upward. 



The trochantero-femoral joint of the insect leg, though usually 

 having little if any motion, is often slightly movable and sometimes 

 freely so, as in the bees. Its movements are always forward and 



Tar 



Fig. 40. — Muscles of right hind leg of Japyx, posterior view (lettering as on 

 fig. 39). 



rearward (production and reduction). In the higher Crustacea, 

 which have two articulated trochanteral segments (basis and ischium, 

 fig. 42 A), the second trochanter and the femur are each provided 

 with productor and reductor muscles (Schmidt, 191 5). In the Chilo- 

 poda and Hexapoda the second trochanter, or the single compound 

 trochanter of most Hexapoda, has no muscles, but it contains a re- 

 ductor femoris (figs. 35, 39, R) inserted on the posterior rim of the 

 femoral base. In the leg of a caterpillar (fig. 41 B) a very small 

 femoral reductor {R) goes from the upper anterior end of the in- 

 complete trochantin {Tn) to the upper posterior part of the base of 

 the femur. In the Protura, Prell (1912) describes a reductor femoris 

 arising within the distal end of the coxa (fig. 41 A, R). Ordinarily 

 the femur has no other muscle than the reductor, but both Berlese 

 (1909) and Prell (1912) describe in the Protura a levator of the 

 femur arising in the base of the coxa (fig. 41 A, //). Berlese describes 

 also a femoral depressor, but Prell does not mention or figure such a 

 muscle. 



