1957 ] Parsons — Esophageal Valve in Hemiptera 139 
Notes on the Esophageal Valve of 
Other Aquatic Hemiptera 
A. Esophagus . 
Since Marks’ description of the histology of the crypto- 
cerate esophagus was brief, a few additional observations 
may be mentioned here. The epithelium 1 consists, as that 
author has stated, of a single layer of cuboidal cells, with 
an inner cuticular intima. It is surrounded by an inner 
circular and an outer longitudinal layer of muscle. 
The present investigation has shown that the histology 
of the corixid esophagus differs somewhat from that of 
Belostoma, Ranatra, and Notonecta. The intima in the latter 
three adheres fairly closely to the esophageal cells ; it gen- 
erally has a scalloped appearance in section, the scallops 
more or less corresponding to the individual cells which 
secrete it. In these three bugs, the esophageal epithelium is 
usually quite folded, the folds projecting into the lumen. 
In Sigara and Hesperocorixa, on the other hand, the epithe- 
lium is less folded and the intima is pulled away from the 
cells, lying free and much folded in the lumen of the eso- 
phagus. In many preparations, the cells appear to be se- 
creting additional layers of intima beneath the ones which 
fill much of the lumPn. 
It has been shown by other authors (Hungerford, 1917 ; 
Griffith, 1945; Sutton, 1951) that the corixids ingest 
particulate matter. In this respect they differ from the 
other Hemiptera, which, as far as has been demonstrated, 
take in only fluids. It may be that the pulling away of the 
esophageal cuticula and the secretion of additional layers 
beneath it is a protective phenomenon, shielding the epithe- 
ilum from abrasion by particles. 
The histology of the esophagus of Pelocoris resembles 
that of the fluid-feeding water bugs rather than that of the 
corixids. Although Sutton found that Naucoris cimicoides 
was able to ingest solid food, no particulate matter was 
observed in any of the Pelocoris guts in the present study. 
