THE SOLDIER OF THE ANT 
CAMPONOTUS ( COLOBOPSIS ) FRAXINICOLA 
AS A TROPHIC CASTE* 
By Edward O. Wilson 
Museum o-f Comparative Zoology Laboratories, 
Harvard University, Cambridge, Massachusetts 02138 U.S.A. 
Complete dimorphism, defined as the coexistence of a minor worker 
of ordinary proportions with a larger major worker or “soldier,” 
represents the pinnacle of the subcaste system within the ants. The 
soldier not only weighs more but also possesses a disproportionately 
larger head. By definition, intermediate forms are lacking. Complete 
dimorphism has originated independently at least seven times, within 
the following genera: the myrmicines Pheidole, Oligomyrmex , 
Acanthomyrmex, Paracryptocerus; the dolichoderine Zatapinoma; 
and the formicines Camponotus and Pseudolasius. The head shapes 
of the major workers of these groups are clearly modified either for 
fighting or for defense of the colony by blocking the nest entrances. 
These functions have been confirmed by direct observations of col- 
onies of Pheidole , Paracryptocerus , and Camponotus (Wilson, 1971). 
The behavioral repertory of the major workers is otherwise very 
limited in comparison with that of the minor workers, giving logic 
to their alternate designation in the literature as soldiers. 
The principal purpose of this article is to demonstrate that in at 
least one species, Camponotus ( Colobopsis ) fraxinicola M. R. Smith, 
the soldier caste also plays a key role in liquid food storage. 
Materials and Methods 
Colonies were collected at St. Mark’s Lighthouse and Tall Tim- 
bers, near Tallahassee, Florida. The taxonomic identification re- 
quires a brief note. Three forms of the southeastern United States, 
fraxinicola , impressus , and pylartes , are very similar to each other 
and may prove synonymous. The Tallahassee series fall closest to 
fraxinicola in the seemingly best character states of the major worker: 
a slightly more flattened mesonotum, more rounded posterior rim of 
the truncated portion of the head, and in other, more subtle details 
of head shape. But all of these characters vary widely within and 
among series 'from widespread localities, so that eventually only one 
*Manuscript received by the editor February 28, 1974. 
182 
