150 
Psyche 
[June 
Fig. 20. H. interrupta; internal view of pterothorax and anterior abdomen, cut 
parasagittally lateral to mesocoxa. Cross-hatched cut edge of mesothoracic pleural 
ridge (PL II) indicates base of pleural apophysis (removed). Metacoxa and soft 
tissues removed; part of inner wall of metathoracic epimeral lobe (EML) removed 
to show outer wall of lobe. 
edge of each mesothoracic epimeron. In Hesperocorixa and Dia- 
prepocoris the ostiole (Figs. 5 and 7, O) lies posteromedially on 
this sclerite. The edge of the epimeron which is immediately lateral 
to it lacks hydrofuge hairs and resembles the “evaporating surface” 
of Gelastocoris (Gelastocoridae; Parsons 1960). In Micronecta 
the ostiole occurs far more laterally on the epimeron, at the posterior 
end of the lateral epimeral lobe (Figs. 6 and 16, O). The edge of 
the epimeron which lies lateral to it possesses hydrofuge hairs and 
is triangular, its apex pointing posteriorly. 
The efferent canals leading to the ostioles also differ in the three 
corixids. In Hesperocorixa and Diaprepocoris the canals are 
deep, open channels which extend anteromedially on each meta- 
thoracic episternum (Figs. 5 and 7, EC). They have a similar form 
in such other Hydrocorisae as Gelastocoris (Parsons 1960), Ilyocoris 
(Naucoridae; Staddon and Thorne 1973) and Notonecta (Noto- 
nectidae; Staddon and Thorne 1974). In Micronecta, however, 
the canals are not externally visible on the metathoracic episternum; 
they are closed ducts which lie immediately beneath the surface of 
