THE MORPHOLOGY OF THE PROVENTRICULUS 
OF A FORMICINE ANT 
By T. Eisner and E. 0. Wilson 
Biological Laboratories, Harvard University 
The ant proventriculus is a structure of considerable 
entomological interest. It is most elaborately developed 
in those groups of ants which have the highest form of 
social behavior and has been generally thought to be as- 
sociated in some way with food storage and trophallaxis. 
It has been used extensively as a taxonomic character in 
the classification of higher categories in the Dolichoderinae 
and Formicinae and in phylogenetic speculation concerning 
these groups. Yet, despite several involved descriptions 
of the anatomy of this organ that have appeared in the 
past, its function and activity have never been properly 
understood. The following paper contains the results of 
a concentrated study of the morphology of the proven- 
triculus of one typical species of formicine. An emphasis 
has been laid on those details that appear to be relevant 
to its function, and there is offered a new explanation of 
its mechanics. 
The first accurate anatomical study of the dolichoderine- 
formicine proventriculus was that of Forel (1879). Emery 
(1888) followed up Forel’s work in a classic comparative 
monograph which is still the basic reference on this organ. 
He reviewed most of the dolichoderine and formicine 
tribes, as well as the aberrant myrmicine tribe Cephalotini. 
Additional brief descriptions of the proventriculus of the 
Dolichoderinae and Formicinae were given in 1912 and 
1925, respectively, in the fascicles of Wytsman’s Genera 
Insectorum dealing with those groups. The most recent 
research on the formicine proventriculus is that of Forbes 
(1938), whose account is mostly a review of earlier work 
and adds little information of significance. 
The ant chosen for the present study was Camponotus 
americanus Mayr. This species proved especially amenable 
to this type of anatomical work, since it is large and 
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