1957 J Parsons — Esophageal Valve in Hemiptera 147 
a distinct groove here, and the sillon is obscured by the 
close approximation of the whorl of annular cells with the 
anteriormost midgut cells. 
The evidence cited by Sutton to support her theory of a 
Type II peritrophic membrane in the corixid ancestor 
appears to be two-fold : the presence of a distinct sillon in 
about half of her specimens, and the existence of a non- 
secretory perivalvular region in all of them. The present 
study casts considerable doubt upon her first piece of evi- 
dence, since the true sillon of corixids is not a distinct 
groove. Her observation of a non-secretory perivalvular re- 
gion in corixids was correct, however, and will be discussed 
in a later paper. Whether or not this is sufficient evidence 
to support the idea that the corixids once secreted a Type 
II peritrophic membrane is difficult to say; it may be that 
the lack of a secretory function in this area is due to other 
causes. Certainly her theory that the long esophageal in- 
vagination is a device for keeping food out of this region is 
open to question ; long valves are present in Anasa tristis 
(Breakey, 1936) and the cacao capsid bug (Goodchild, 
1952), neither of which has a non-secretory perivalvular 
region. 
Literature Cited 
Aubertot, M. 
1934. Recherches sur les peritrophiques des insectes et en particulier 
des Dipteres. Theses: Fac. Sci. Univ. Strasbourg. 
Breakey, E.P. 
1936. Histological studies of the digestive system of the squash bug 
(Anasa tristis DeG. Hemiptera, Coreidae). Ann. Ent. Soc. Amer.. 
29:561-577. 
van Gehuchten, A. 
1890. Recherches histologiques sur l’appareil digestif de la Ptychop- 
tera contaminata. 1. Part. Etude du revetement epitheliale et re- 
cherches sur la secretion. La Cellule, 6:185-289. 
Goodchild, A.J.P. 
1952. A study of the digestive system of the West African cacao cap- 
sid bugs. Proc. Zool. Soc. Lond., 122:543-572. 
Griffith, M.E. 
1945. The environment, life history, and structure of the water boat- 
man Rhamphocorixa acuminata (Uhler) (Hemiptera, Corixidae). 
L T niv. Kans. Sci. Bull., 30:241-365. 
