1976] Bowdan — Functional Anatomy of Gerris remigis 299 
Figure 6: Diagrammatic representation of the articulation of the trochanter 
on the coxa, and of the actions of muscles 46, 47 and 50 on the mesothoracic 
leg of G. remigis. 
a) articulation of the trochanter on the coxa 
a m 
articular membrane 
a n 
coxal articular notch 
d r 
distal rim of coxa 
f 
femur 
tr 
trochanter 
tr cond 
trochanteral condyle 
b) resting position of the leg 
c) contraction of muscles 46 + 47 causes the leg extremities to go backwards 
(retract). 
d) contraction of muscle 50 causes the extremities to go forward (protract), 
p a pivotal axis 
— » direction of the major component of the muscles’ force. 
Note that a) has an orientation which is different from that of b), c) and d). 
