THE INFRABUCCAL POCKET OF A 
FORMICINE ANT: A SOCIAL FILTRATION DEVICE 1 
By T. Eisner and G. M. Happ 
Department of Entomology, Cornell University 
The importance of regurgitative feeding as a means for distributing 
liquid nutrient among workers, and from workers to larvae and queen, 
has long been recognized, and it is now generally agreed that this 
process is a most fundamental bond in the social life of many ants 
(Le Masne, 1953; Wallis, 1961 ; Wheeler, 1923; Wilson and Eisner, 
1957). Unlike honeybees, which also feed one another by regurgita- 
tion, but which have their principal food reservoir outside their own 
bodies in the honeycomb, ants store liquids exclusively within the crops 
of the individual living workers. Crop storage and regurgitative feed- 
ing are probably most highly developed in the specialized and success- 
ful subfamilies Formicinae and Dolichoderinae. It is in these ants that 
the crop is most capacious (witness the fact that ants with “replete” 
castes are restricted to these subfamilies), and it is these that have a 
special device, in the form of an elaborately refined proventriculus, 
adapted to dam the posterior outlet of the distended crop (Eisner, 
1957; Eisner and Brown, 1958). 
In its basic features, the proventriculus of Dolichoderinae and For- 
micinae is really no different from that of other ants and of Hymenop- 
tera in general. It is a mechanical pump, consisting of a strongly 
muscled bulb, with an anterior intake valve communicating with the 
crop, and a posterior outlet valve leading to the midgut. When 
nutrient is to be passed from foregut to midgut, the bulb is put into 
operation, and through a series of rhythmic compressions and decom- 
pressions, liquid is effectively pumped along. Whereas in most Hymen- 
optera the intake valve of the proventriculus is a more or less mobile 
portal, incapable of effective prolonged closure, and hence ill-adapted 
to withstand for protracted periods the liquid pressure from a filled 
crop, in formicine and most dolichoderine ants the portal valve is 
permanently restricted to a narrow cruciform cleft through which 
leakage of crop contents is virtually impossible. It is only during 
proventricular pumping that liquid is passed through the clefts under 
This study was supported in part by Grant E-2908 of the U. S. Public- 
Health Service. 
Manuscript received by the editor February 16, 1962. 
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