298 
Psyche 
[September- December 
Figure 5: Lateral view of the coxa and trochanter of G. remigis. Diagram to 
illustrate the activity of muscles 40 and 41 in respectively lowering b) and rais- 
ing c) the extremities of the leg. 
c g point of emergence of the coxa from the coxal groove 
p c position of the pleurocoxal attachment 
r a axis of rotation 
tr trochanter 
of locomotion. Two such animals are Gelastocoris ocu/atus, 
the toad bug (Parsons, 1960) and Belostoma flumineum, the 
giant water bug (Segal, 1962). 
The mesothoracic coxae of Belostoma and Gelastocoris are 
less concealed by the supracoxal lobes, which are smaller than 
those of Gerris. These coxae therefore have more freedom of 
movement and also possess an additional coxal rotator (muscle 
42). The coxae of Belostoma and Gelastocoris have rotated some- 
