1976] Bow dan — Functional Anatomy of Gerris remigis 
295 
Figure 3: Right coxa and trochanter of G. remigis to show the articulation 
of the trochanter on the coxa 
a m articular membrane 
c coxa 
c a c coxal articulation for the trochanteral condyle 
tr trochanter 
tr c one trochanteral condyle, the other is directly opposite as shown in the 
diagram of Fig. 6. 
Functions of the Muscles 
The role of the coxal and trochanteral muscles can be inferred 
from a knowledge of their origins and insertions and of the ar- 
ticulations of the coxa and trochanter. These inferences have 
been confirmed by electrophysiological information from the 
muscles recorded simultaneously with monitoring of the leg 
movement (Bowdan, 1977). 
Muscles 40 and 41 are antagonists and pivot the coxa around 
its anterior/ posterior axis. In doing so they also lower and raise 
the extremities of the leg (Fig. 5). Contraction of muscle 40 ro- 
tates the coxa so that its dorsal aspect comes to lie laterally. 
The distal portion of the leg is lowered by this action (Fig. 5b). 
Contraction of muscle 41 rotates the coxa in the opposite direc- 
