120 
Psyche 
[December 
The peritrophic membrane of Ranatra bears some re- 
semblances to that of Sigara falleni and Corixa punctata as 
described by Sutton (1951). Both were of Wigglesworth’s 
Type I, fragmentary in nature, and seemed to be secreted 
in response to the presence of food ; both were present in 
only a few of the individuals examined. Sutton found the 
peritrophic membrane only in the posterior part of the 
midgut, however, whereas that of Ranatra may occur 
throughout the mesenteron. 
The author has examined several species of North Amer- 
ican corixids, representing the genera Hespero corixa, Si- 
gara , and Trichocorixa, to determine whether any of these 
possessed a peritrophic membrane. Histological sections 
through the midguts of ninety corixids showed no evidence 
of a membrane. The midguts of ninety-nine others, all of 
which contained food, were removed and examined in a 
dish of Ringer’s solution under a stereoscopic microscope; 
they were carefully turned inside out, beginning at the 
posterior end, with fine forceps. Since the epithelium tended 
to curl outwards when peeled back in this way, its inner 
surface and the surface of the midgut’s contents could be 
easily examined for traces of a membrane. However, none 
of the midguts so examined showed anything of this sort. 
The two species of which the most individuals were ex- 
amined were Hesperocorixa interrupta (113) and Sigara 
signata (22) ; the present study has shown, therefore, that 
a peritrophic membrane is absent, or at least extremely 
rare, in these species. 
Sutton applied the Schulze and chitosan tests to whole 
midguts, using the technique which was described earlier 
in this paper. She considers the chitosan test to be the most 
reliable, and describes her method as follows: “I did not 
dissect out the membrane. Instead I dissected out the hind 
part of the mid gut taking great care that no trace of the 
oesophageal valve was present (to avoid any invalidation 
of the results of the tests to be applied, by the chitinous 
‘entonnoir’.) The chitosan and Schulze tests were then 
applied to the freshly dissected mid guts. I did not apply any 
test for chitin to preserved material” (Sutton, personal 
comlmunication) . 
