524 
Psyche 
[September -December 
Thorpe and Crisp (1947c) have described how the elongated 
setae on the abdominal sense organs of A pKelocheirus become com- 
pressed under increased pressure, stimulating shorter sensory hairs 
which are interspersed among them, and thus warning the insect 
against diving to dangerous depths. The elongated leaf-like setae on 
the six pairs of abdominal sense organs of Cryphocricos probably 
have a similar function, and the shorter leaf-like setae on the rest 
of each paratergite may have evolved from these longer ones. 
The efficiency of the plastron in Cryphocr'cos cannot be deter- 
mined without experiments similar to those which Thorpe and Crisp 
(1947a, 1947b) performed on A phelocheirus. Nearly all of the 
ventral surface of Cryphocricos , and at least a part of the exposed 
dorsal surface, bear apparent hydrofuge devices. If these devices do, 
indeed, retain a thin, permanent, plastral air layer, a considerable 
surface area of air is exposed to the water and is capable of gas ex- 
change with the latter. Dissolved oxygen could pass directly to the 
mesothoracic, metathoracic, and second through eighth abdominal 
spiracles, all of which face portions of the ventral plastron. Although 
the dorsal subalar space is not exposed to the water, it communicates 
with the ventral air layer by means of the narrow gap between the 
ventrally exposed portion of the forewing (Fig. 1, FW) and the 
ventrolateral edge of the body. The hydrofuge hairs l ning this gap 
would permit a small amount of oxygen to pass from the ventral 
plastron to the first abdominal spiracle, which faces the subalar space 
(Parsons 1974). The extent to which the spiracles, especially the 
first abdominal ones, are capable of inhalation is not known, however, 
and will require experimentation and further fine-structural studies. 
There is a . strong possibility that well-developed plastral respira- 
tion has evolved in other Naucoridae, as Hinton (1969a) claims. 
Further investigation will probably reveal it not only in other mem- 
bers of this family but quite possibly in other families of aquatic 
Heteroptera as well. 
Fig. 11. C. barozzii; shin,gle-like arrangement of several groups of 
microtrichia on median portion of fourth abdominal sternite, approximately 
midway between its anterior (towards top) and posterior (towards bottom) 
boundaries. Arrow indicates where tips of hairs, mostly concealed by debris, 
appear to be interspersed among groups of microtrichia. Scale line = 5 ^m. 
Fig. 12. C. barozzii; large numbers of fringed setae on lateral edge of 
sixth ventral abdominal paratergite, left side of body. Arrow indicates 
edge of body. Scale line = 10 |Um. 
