1976] 
Parsons — Morphology of Corixidae 
169 
The air stores in Diaprepocoris and Micronecta appear to be at 
least as substantial as those of Hesperocorixa. All three insects 
possess large concealed air stores (subalar, cervical, and I-II) as 
well as an extensive ventral air layer which, being exposed to the 
water, is presumably able to obtain dissolved oxygen. Diaprepo- 
coris is smaller than Hesperocorixa and has additional exposed air 
layers on the mesonotum and on most of the forewing, rather than 
only on the emboliar region. Micronecta has the advantage of very 
small size and, consequently, a large surface in proportion to its 
volume. Diaprepocoris and Micronecta thus appear to be at least 
as capable as Hesperocorixa of utilizing dissolved oxygen. 
Thorpe and Crisp (1949) grouped aquatic insects with hydrofuge 
hairs into four categories, ranging from Group I (those with true 
plastral hairs) to Group IV (those with hairs which merely protect 
them against accidental wetting). Thorpe (1950) placed Corixa 
(Corixinae) in Group III, members of which must come to the 
surface at intervals to obtain atmospheric air and which are buoyant 
rather than heavier than water. Insects of Group III often possess 
a double hair pile, with a “macroplastron” of long hairs and a much 
thinner “microplastron” of short hairs (Thorpe and Crisp 1949). 
Hesperocorixa, like Corixa, clearly belongs in this category. 
The similarity of the long and short hairs of Hesperocorixa to 
those of Diaprepocoris and Micronecta strongly suggests that all 
three insects have a similar mode of respiration. Leong (1961) 
and Wroblewski (personal communication) note that Micronecta 
periodically comes to the surface of the water for air although, 
according to Wroblewski, it can remain submerged during times 
of strong wave action, presumably utilizing dissolved oxygen dur- 
ing these occasions. Wroblewski also points out that Micronecta 
requires well-aerated aquaria. Although I could obtain no be- 
havioral information on Diaprepocoris, the presence of a macro- 
plastron of long hairs on its ventral abdominal surface would indi- 
cate that it is an air-bubble insect rather than a true plastral insect. 
The Corixinae, unlike other Hydrocorisae, renew their air stores 
by contacting the surface of the water anterodorsally and taking 
in the atmospheric air beneath the long pronotum and the flange- 
like posterior edge of the head. To my knowledge it is not known 
whether the Deaprepocorinae and Micronectinae share this method 
of obtaining air or whether they contact the surface of the water 
with the tip of the abdomen, like most Hydrocorisae. Although the 
