138 
Psyche 
[December 
Vacuoles similar to these may be seen in the cells at the 
tip of the invagination in Hesperocorixa and Sigara, but 
they are rarely found in Belostoma, Notonecta, or Ranatra. 
This suggests that they may be associated with the pulling 
away of the cuticula to form the entonnoir, a phenomenon 
found in corixids and in Pelocoris but not in the other three 
bugs. Vacuolated cells have been described in the esophageal 
valves of Ptychoptera contaminata (van Gehuchten, 1890), 
and in two species of aphids (Weber, 1928, and Miller, 
1932), all of these having a cuticula which is somewhat 
separated from the cells of the invagination. 
Sutton, after examining Naucoris cimicoides, concluded 
that there are two “varieties” of that species. The first of 
these, she stated, has a “long oesophageal valve” (Sutton, 
1951, p. 489; she did not say how long), with a shorter 
entonnoir than that found in corixids, and possesses a de- 
finite corixid-like “proventriculus”. The latter term is mis- 
leading, since it has been used by some authors to designate 
the “gizzard” of the foregut; in the present study, the 
“proventriculus” of Sutton, which is part of the midgut, 
will be called the “perivalvular region”. In corixids it sur- 
rounds the esophageal invagination (Text-fig. 3), and is 
narrower in diameter than the more posterior part of the 
midgut, from which it is separated by a constriction. No 
such perivalvular region was found in any of the naucorids 
examined in this study. 
Sutton found a second “variety” of Naucoris cimicoides 
in which there is no distinct perivalvular region and the 
esophageal valve is reduced to a vestige. In Pelocoris, all 
the esophageal invaginations appeared to be equally prom- 
inent. Whether Pelocoris is more similar to the first “va- 
riety” or the second “variety” of N. cimicoides cannot be 
definitely determined, since Sutton did not include illustra- 
tions of the valves of both of these; the lack of a differen- 
tiated perivalvular region in Pelocoris, however, suggests 
that it more closely resembles the second “variety”. This 
theory is supported by the conclusion of Marks (in press) 
that the food pump of Pelocoris bears more similarity to the 
second “variety” of N. cimicoides than to the first. 
