164 
Psyche 
[June 
Fig. 28. H. interrupta; detail of external surface of sieve-plate on right meta- 
thoracic spiracle. Branching trabeculae are connected by short struts to an inner 
membrane which bears pinnately-arranged narrow slits. Dorsal margin of integu- 
mental region appears at extreme lower left. Top of figure is dorsal, right side is 
anterior. Scale line = 10 /urn. 
Fig. 29. D. zealandiae; external surface of anterodorsal part of metathoracic 
spiracle, oriented as in Fig. 25. Sieve-plate bears branching trabeculae; inner mem- 
brane is too deep to be visible. Surface of mesothoracic epimeron (upper and lower 
right) is covered with short hydrofuge hairs. IN = integumental region of spiracle, 
with irregular folds. Top of figure is dorsal, right side is anterior. Scale line = 10 /urn. 
G. Mesothoracic Scolopophorous Organ 
The mesothoracic, metathoracic, and first abdominal scolopo- 
phorous organs of most Hydrocorisae consist of a sensory mem- 
brane which bears a very small sclerite for the attachment of a 
two-celled scolophore (Larsen 1957). In the Corixidae, however, 
the mesothoracic scolopophorous organ, unlike the metathoracic 
and first abdominal ones, bears a large sclerite, which is modified 
in different ways in the three forms here examined. 
