174 
Psyche 
[June 
Diaprepocoris. The degree of continuity between the first abdomi- 
nal spiracular chamber and the air layer surrounding the metacoxa 
also differs in the three insects; it is greatest in Diaprepocoris (Fig. 
22, black arrow), more limited in Micronecta (Fig. 23, black arrow) 
and very limited or absent in Hesperocorixa (Fig. 25). 
Finally, the anterolateral part of the abdomen shows variation. 
All three corixids possess well-developed muscle processes (Figs. 
22-24, MP), but that of Diaprepocoris is separated from, rather 
than fused with, the rest of the abdomen. Both Diaprepocoris 
and Micronecta lack the strongly developed condition of the second 
abdominal antecosta which is present in Hesperocorixa (Fig. 24, 
AC2). 
Summary. 1. Representatives of the three subfamilies of Corixi- 
dae were examined. Although data on the respiration of Diaprepo- 
coris (Diaprepocorinae) and Micronecta (Micronectinae) are 
lacking, the morphology of preserved specimens suggests that they 
use air-bubble respiration like Hesperocorixa (Corixinae). The 
structure of the forewings and intersegmental regions and the dis- 
tribution of the hydrofuge hairs indicate that all three insects possess 
air stores on the ventral surfaces of the abdomen and thorax, be- 
neath the forewings, between the head and prothorax, between the 
prothorax and mesothorax, and on the forewings. Diaprepocoris, 
unlike the other two insects, has an exposed air layer on the meso- 
notum and a supra-alar air layer covering nearly all of the forewing. 
2. Hesperocorixa obtains atmospheric oxygen by periodically 
contacting the water surface anterodorsally, taking air into the 
air spaces beneath the head and pronotum. It appears likely that 
Diaprepocoris and Micronecta share this mode of behavior. All 
three insects can also obtain dissolved oxygen by means of the 
“physical gill” effect of their exposed air stores. 
3. Of the three corixids examined, Diaprepocoris shows the fewest 
pterothoracic modifications and Hesperocorixa shows the most. 
The mesothoracic epimeron of Diaprepocoris is not widened like 
that of the other two insects, and Diaprepocoris lacks a specialized 
metathoracie “air trough”. The mesothoracic scolopophorous or- 
gans of all three corixids differ from those of other Hydrocorisae. 
Those of Diaprepocoris and Micronecta possess one and two large 
sclerites respectively while that of Hesperocorixa has two sclerites 
