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Psyche 
[June 
were available for the present study, the location of their air stores 
can be deduced from their morphology, particularly the distribu- 
tion of hydrofuge hairs on the body. These hairs, which are clearly 
visible under the scanning electron microscope, can conveniently 
be divided into two categories according to their length. 
The long hairs (Figs. 1-3) range from 20 to 70 jum in length and 
are shorter in Micronecta (20-40 pm) than in the other two corixids. 
They are from one to five pm in diameter basally, and taper termi- 
nally. In Diaprepocoris and Hesperocorixa most, if not all, of the 
long hairs bear spiral grooves (Figs. 1 and 2); although those ol 
Micronecta may have similar grooves they were not visible in any 
of the photomicrographs. When closely-packed, as on the abdo- 
men of Hesperocorixa (Fig. 1), the long hairs are capable of holding 
a relatively thick air layer or “macroplastron” (term of Thorpe and 
Crisp 1949). 
The short hairs (Figs. 2-4), unlike the long ones, are visible only 
under the scanning electron microscope and are much more densely 
packed. They range from two to ten jum in length and from 0.35 
to 0.55 pm in diameter, and their tips are strongly curved. In many 
photomicrographs of Micronecta, and in occasional ones of Hes- 
perocorixa, the short hairs have the appearance shown in Fig. 3; 
they resemble low arches, with several branch-like ribs, rather than 
separate hairs. It is not clear whether these arches are artifacts 
caused by the clumping of the tips of short hairs during preparation 
for the scanning electron microscope, or whether they represent 
a different type of hydrofuge structure. 
II. Ventral Air Store 
The ventral surfaces of the thorax and abdomen are covered with 
hydrofuge hairs in all three corixids. The ventral abdominal 
surfaces bear closely-packed long hairs which are approximately 
9 to 23 pm apart in Micronecta and 13-18 pm apart in Diapre- 
pocoris and Hesperocorixa. A conspicuous, thick ventral abdom- 
Figs. 1-4. Hydrofuge hairs; tops of figures are anterior. Fig. 1. Hesperocorixa 
interrupta; long hairs on ventral surface of third abdominal segment in region of left 
third abdominal spiracle (right side of figure). Scale line = 10 pm. Fig. 2. Diaprepo- 
coris zealandiae; short hairs and parts of three spirally-grooved long hairs on external 
surface of corium of forewing. Scale line = 5 ^m. Fig. 3. Micronecta sedula, short 
hairs and parts of three long hairs on ventral surface of right prothoracic epimeron. 
Note arched appearance of most short hairs. Scale line = 5 pm. Fig. 4. H. inter- 
rupta; short hairs on ventral surface of right prothoracic epimeron. Scale line = 2 jum. 
