1957 ] Parsons — Esophageal Valve in Hemiptera 141 
B. Esophageal Valve 
1. Location of the Muscle 
In their studies of the esophageal valve of corixids, both 
Sutton and Marks described circular muscle strands within 
the intravalvular space of the invagination. In the present 
study, muscle was absent in this area in all 36 corixids exa- 
mined. The muscle is limited to a strongly developed sphinc- 
ter at the point where the esophagus enters the midgut 
(Text-fig. 3) and a less well developed longitudinal layer 
overlying this sphincter. 
It is the author’s belief that the “muscle strands” of 
Sutton and Marks were only fine connective tissue fibers; 
these are very com'mon in the subepithelial tissue of the 
gut, and appear to run between the basement membrane 
of the epithelium and the sarcolemma of the muscle. Such 
fibers have been described in the connective tissue sur- 
rounding the gut of other insects (Rengel, 1896; Nazari, 
1899; Leger and Duboscq, 1902). In the corixids, these 
connective tissue fibers, along with small tracheoles, pen- 
etrate the intravalvular space of the esophageal invagina- 
tion, and may quite easily be mistaken for muscle strands 
(Mr. Marks has examined my material, and agrees with 
this conclusion). 
2. The Annular Cells 
In all five bugs, the junction of the foregut and midgut 
is encircled by a ring of tall foregut cells. These correspond 
to the “terminal pad” of Marks, who showed them in his 
figures of Hesperocorixa, Belostoma, Ranatra , and Noton- 
ecta. Sutton apparently mistook them for midgut cells, as 
Marks has pointed out. 
Text-figure 3 shows the location of the annular cells in 
Sigara and Hesperocorixa. The annular cell region in cor- 
ixids is more extensive than Marks’ figures (1958, his plate 
VII, figures 1, 3, and 4) would indicate; the author has 
examined Marks’ slides, and found that this region showed 
some distortion in his material, which probably accounts 
for this difference. 
The most outstanding feature of the annular cells, which 
was overlooked by both Sutton and Marks, is their high 
