1976] Parsons — Morphology of Corixidae 133 
compared with that of representatives of the other two subfamilies, 
whose respiration has never been investigated. The fine structure 
of the hydrofuge hairs and of the metathoracic and first abdominal 
spiracles, which has not yet been studied in any of the Corixidae, 
is also compared in Hesperocorixa, Micronecta (Micronectinae), 
and Diaprepocoris (Diaprepocorinae). 
The Corixinae differ markedly from other Hydrocorisae in many 
morphological features. Their unusual characteristics include the 
very complex mesothoracic scolopophorous organ (“Hagemann’s 
organ” of many authors), the modified mesothoracic and meta- 
thoracic epimera, the elongation of the pronotum and the posterior 
margin of the head, the metathoracic “air trough”, and the unusual 
position of the metathoracic and first abdominal spiracles (Parsons 
1970, 1974). These characteristics are compared in representatives 
of all three subfamilies, and their phylogenetic implications are 
discussed, below. 
B. Materials and Methods 
Observations were made on Hesperocorixa interrupta (Say) 
from Massachusetts and Ontario, Diaprepocoris zealandiae Hale, 
from New Zealand, and Micronecta sedula Horvath, from Fukuoka, 
Japan. The insects, preserved in ethanol or Bouin’s fluid, were 
dissected in 80% ethanol under a stereoscopic microscope. 
For examination under the scanning electron microscope, speci- 
mens were transferred, through decreasing concentrations of etha- 
nol, to distilled water. They were then mounted on aluminum stubs 
with silver Electrodag and kept briefly in distilled water until they 
were freeze-dried in an Edwards Speedivac-Pearse Tissue Drier, 
Model 1. They were coated with 20-40 nm of gold in an Edwards 
Vacuum Evaporator, examined under a Cambridge Stereoscan, 
Model 2A, and photographed with Kodak Verichrome Pan 120 
roll film. 
C. Air Stores 
I. Hydrofuge hairs 
The distribution of the air stores in living specimens of Hespero- 
corixa was described in an earlier study (Parsons 1970). There are, 
to my knowledge, no similar descriptions of the air stores of Dia- 
prepocoris, and Leong (1961) mentions those of Micronecta only 
briefly. Although only preserved specimens of all three corixids 
