1976] Bowdan — Functional Anatomy of Gerris remigis 291 
(distal) end leaves the thorax by a circular opening close to the 
metathorax. The lateral wall of this opening is formed by the 
supracoxal lobes. The coxal groove and small, backwardly pro- 
jecting opening severely restrict coxal movement. The only pos- 
sible movement is a rotation about the anterior / posterior axis 
between the pleurocoxal attachment and the opening. The proxi- 
mal coxal rim has a medial trochantin and a lateral apodeme 
on to which muscles 40 and 41, respectively, insert. The distal 
third of the coxa is outside the body cavity and is more rounded 
than the proximal two thirds. 
The next segment, the trochanter, is also highly modified. It 
is a little shorter and rather slimmer than the coxa (Fig. 3). The 
medial proximal rim is extended into several large apodemes 
on to which muscles 46 and 47 insert. Muscle 50 inserts on a 
smaller lateral apodeme. The trochanter articulates with the 
coxa by means of a dicondylic joint. This forms the axis about 
which muscles 50 and 46 plus 47 act antagonistically and is in 
the dorso/ ventral plane. As the trochanter leaves the coxa, it 
makes a sharp, right-angled turn so that the surface which was 
medial in the proximal part of the segment is the posterior sur- 
face in the distal part of the segment (Fig. Id). 
The femur is fused directly to the trochanter and so has no 
independent movement. It consists of a smple cylinder, a little 
longer than 1 cm. The femoro-tibial joint has been described 
in great detail by Darnhofer-Demar (1973) and is a simple hinge. 
The tarsus is two-segmented and has two, backwardly directed, 
subapical claws. The exposed parts of each segment are covered 
with a variety of sensory hairs (Weber, 1930; Lawry, 1973), which 
are doubtless of importance in orientation during courtship 
(Wilcox, 1972) and capture of prey (Murphey, 1971). 
Muscles 
The mesothorax is by far the largest segment of the body, oc- 
cupying about one third of the length of the body. Its muscula- 
ture has already been described in detail by Larsen (1945), for 
G. rufoscellutus, and by Guthrie (1961) and Darnhofer-Demar 
(1969) for G. lacustris. For convenience it will here be described 
briefly for G . remigis. For reasons of historical precedence and 
to facilitate comparison of gerrids with other Heteroptera, Lar- 
sen’s numbering system is used here. A comparison of nomen- 
