48 
Psyche 
[June 
possesses a translucent integument. The crop, when filled 
with stained fluid, can be observed through the gastric 
tergites, so that those individuals that have their crops 
distended most suitably for dissection can easily be picked 
from the artificial nests. China ink was found to be the 
most suitable of several stains considered for use in study- 
ing the course of food in the living gut. This was ground 
up in honey to make an intensely black liquid, which could 
be traced even when passing through the fine canal system 
of the proventriculus. Dissections were accomplished 
simply by clipping the ant’s legs, removing the sternites 
with a fine pair of scissors, picking out the fat body, and 
washing the cavity of the gaster with insect Ringer’s 
solution. For histological studies the gut was serially 
sectioned at seven microns and stained with Ehrlich’s 
haemotoxylin and eosin. 
Text-figure 1. Soldier of Camponotus americanus Mayr, with a 
window cut in the gaster to show size and placement of the proven- 
triculus. Cr, crop; pv, proventriculus; mg, midgut. 
The proventriculus, or gizzard, lies in the anterior half 
of the gastric cavity when not displaced posteriorly by 
the distended crop (text— fig. 1.). It is the last segment 
of the foregut and connects the usually voluminous crop 
with the midgut. In the “euformicine” ants (section 
Explanation of Plate 5 
Exploded semidiagrammatic drawing of the chitinous framework 
of the proventriculus. Epithelium and muscularis not shown. A. calyx; 
B, occlusory tract; C, bulb; D. cylinder. Sep. cnl., sepal canal; filt., 
filtering slit of sepal; sep., sepal; in., intersepalary intima; cyl. vlv., 
cylinder valve. (180X) 
