290 
Psyche 
[September-Decernber 
this both to other Heteroptera and to the mode of locomotion 
of G err is remigis. 
Materials and Methods 
Animals were collected from local streams in western Massa- 
chusetts. Mesothoracic anatomy was studied by conventional 
dissections of specimens preserved in 70% alcohol. Nerves were 
traced in animals which had been injected with a 1% solution 
of methylene blue in Insect Ringer (Becht, Hoyle and Usherwood, 
1960) shortly before they were killed. 
Results 
Skeleton of the Leg 
The mesothoracic leg consists of the usual five segments, but 
some have become highly modified. The coxa, the most proxi- 
mal segment, is about 2.5 mm long. In comparison with the coxae 
of most insects (Snodgrass, 1935) the gerrid coxa has rotated 
so that the coxal dorso/ ventral axis of most insects has become 
the anterior/ posterior axis in the gerrid coxa (Fig. la, b). The 
proximal two thirds of the coxa lies within the coxal groove in 
the mesothoracic cavity (Fig. 2). The base of the coxal groove 
is formed by the sternum and the lateral walls consist of the supra- 
coxal lobes of the well developed epimeron and episternum. The 
anterior end of the coxa is attached to the pleuron by a heavily 
sclerotized region, the pleurocoxal attachment, and the posterior 
TABLE 1 
MESOTHORACIC MUSCLE NOMENCLATURE AS USED BY LARSEN 
(1945), GUTHRIE (1961) AND DARNHOFER-DEMAR (1969). 
Guthrie 
. lacustris 
Darnhofer-Demar 
G. lacustris 
Larsen 
G. rufoscutellatus 
52 
M. mesonoto trochanteralis 
46 M. nototrochanteralis 
52 
M. mesopleurotrochanteralis 
47 M. pleurotrochanteralis 
53 
M. mesonototrochantinalis 
41 M. nototrochantinalis 
54 
M. mesonotomerocoxalis 
40 M. notocoxalis 
M. mesocoxa - trochanteralis 
lateralis 
50 M. coxa - trochanteralis 
lateralis 
