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Parsons — Morphology of Corixidae 
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wing, the metathoracic epimeron, and the anterolateral part of the 
abdomen (Figs. 1 1 and 12, arrow) which allows the subalar air store 
to communicate with the ventral one. The two air stores probably 
also communicate along the posterior part of the abdomen, which 
bears lateral setae (Figs. 5 and 6, right sides of figures). 
D. Pterothorax 
I. Typical Hydrocorisae 
The pterothorax of typical Hydrocorisae has been described in 
previous publications (Parsons 1970, 1974) and will be only briefly 
summarized here. 
The mesothoracic (Fig. 14 A, EM II) and metathoracic episternum 
(ES III) form flat evaginated lobes laterally, posteriorly, and pos- 
Fig. 14A and B. Diagrammatic lateral views. (A) Pterothorax and anterior 
abdomen of typical Hydrocorisae. Mesothorax cut transversely, wings removed 
posterior to transverse cut. Heavy broken line indicates position of lateral inter- 
segmental boundary, concealed by external wall of mesothoracic epimeron (EM II); 
heavy stippling indicates intersegmental air store, which contains metathoracic 
spiracle (concealed in this view). (B) Anterior mesothorax, cut as in Fig. 14A, show- 
ing how lateral epimeral lobe (LL) is modified in M. sedula and H. interrupta. 
