1962 ] 
Eisner and Ilapp — Infrabuccal Pocket 
113 
Another experiment was designed to replicate more closely the 
crowded conditions prevailing in actual nests. A total of 35 ants, fed 
on honey- iO/x corundum and provided with color markings, were 
divided into seven groups of five each, and each group was introduced 
into an observation arena containing 50-75 unfed nestmates. Another 
35 ants, similarly fed, served as controls, and were confined each ant 
by itself. At the end of twelve hours both lots were killed, and a visual 
estimate made of the corundum contents of their individual crops (one 
ant of the first lot escaped). The results (text fig. 1) were strikingly 
different in the two batches. Of the isolated ants, nearly every one had 
the crop filled with corundum to one quarter or more of its capacity. 
Of those that had been confined socially, about half had completely 
clear crops, and in most of the remainder the crops were less than one- 
quarter full with particles. Evidently, in the context of the society, 
debris is rapidly filtered from the communal crop supply. One might 
add that, whereas in each of the arenas containing the ants in groups 
there were found at the end of the 12-hour period a dozen or more 
infrabuccal pellets of corundum, the ants confined singly produced only 
an occasional single pellet. The pellets recovered in the group-tests 
stemmed not only from the five introduced food donors, but were 
actually seen in some cases to have been ejected by residents that had 
received food by regurgitation. (Ants confined singly over a period of 
several days sometimes produced more than one pellet. Since during 
this period they often regurgitated their particle-laden crop contents 
onto the walls of their glass enclosures, the production of more than 
one pellet may signify that their crop loads had undergone a series of 
filtrations as a result of reingestion of the regurgitate. These observa- 
tions may be of no more than incidental interest, since prolonged lone 
confinement is obviously not the rule in nature.) 
DISCUSSION 
The above experiments show the infrabuccal chamber of Campono- 
tus to be an organ of considerable social importance, in that it serves to 
maintain the liquid communal crop supply particle-free. It would be 
interesting to know whether the chamber is a similarly effective filter- 
ing apparatus in other ants. In formicines, and in the more advanced 
dolichoderines, the proventriculi of which are so constructed as to 
preclude passage of solids, one would certainly expect this to be so. 
Since the midgut of these ants is never likely to be exposed to the 
abrasive action of particulate matter, it is noteworthy that a peritrophic 
