1962] 
Eisner and Happ — Infrabuccal Pocket 
1 15 
block the passage of fluid during proventricular pumping. In this 
connection it is of interest that some formicine proventriculi have a 
special device that apparently serves to wipe the clefts of obstructing 
solids (Eisner, 1957). In Camponotus , as well as in other formicines 
with so-called “sepalous” proventriculi, such a device is missing, but 
since the “calyx” of the proventriculus presumably undergoes rhythmic 
constriction and dilation during the pumping cycle (the calyx is 
enveloped by circular muscles), the space within it is likely to be 
stirred sufficiently to prevent particles from accumulating over the 
portal clefts on the sepals (Eisner, 1957). 
In ants of some of the other subfamilies, the infrabuccal chamber 
has been shown to serve special functions. Thus, in Atta and certain 
other fungus growers (subfamily Myrmicinae), the chamber provides 
the receptacle in which a supply of fungal spores is carried from the 
parent colony by the departing nest-founding female that must ulti- 
mately start a new fungus garden of her own (von Ihering, 1898; 
Huber, 1905). In yet another subfamily, the Pseudomyrmecinae, the 
larvae are fed with food pellets compacted in the infrabuccal pockets 
of the workers, which deposit the pellets in a special postoral receptacle 
(trophothylax) of the larva (Wheeler and Bailey, 1920). 
In honeybees, the infrabuccal chamber is apparently inoperative as 
a filter (Snodgrass, 1956). These insects rely on the intake and 
digestion of pollen as a protein source for the subsequent manufacture 
of brood food, and this special requirement can obviously be met only 
in the absence of thorough preoral filtration. Interestingly, the pro- 
ventriculus of honeybees is especially adapted to transmit dense pollen 
suspensions to the midgut without becoming choked (Bailey, 1952) . 
A representative comparative study of the infrabuccal chamber of 
Hymenoptera has never been made. In the absence of such a study, it 
is difficult to speculate on the evolutionary justification for the chamber 
as it first arose within the order. But since adult Hymenoptera are 
predominantly fluid feeders, one may reasonably presume that the 
chamber functioned as a filter from the very outset [its filtering action 
in at least some wasps has been demonstrated by Duncan (1939) and 
Janet (1895b)]. To ants like Camponotus, as well as to all other 
formicines and dolichoderines with an intranidal organization heavily 
dependent on crop storage and regurgitative food transmission, the 
infrabuccal filter is thus seen to represent an evolutionary preadapta- 
tion of considerable importance. In the absence of an adequate preoral 
filtration mechanism by which the communal crop supply is maintained 
particle-free, the proventriculus could not have evolved toward pro- 
