TRAIL SHARING IN ANTS 
By Edward O. Wilson 
Biological Laboratories, Harvard University 
introduction: the kinds of trail sharing 
A very few cases have been recorded of ant workers regularly 
utilizing the trails of other ant species. Forel (1898) designated as 
“parabiosis” the following complex behavior that includes trail 
sharing. Colonies of the Neotropical rain forest species Crematog aster 
limata parabiotica Forel and Monacis debilis (Emery) [ —Doli - 
choderus debilis var. parabiotica Forel] commonly nest in close 
association, with the nest chambers kept separate but interconnected 
by passable openings; while the workers forage along common odor 
trails. Wheeler (1921) confirmed the phenomenon and showed that, 
in the one instance where he observed food gathering, the two species 
were attending membracids together. Wheeler also discovered a 
similar association between Crematogaster parabiotica and Campo- 
notus femoratus (Fabricius). Both species were observed utilizing 
common trails and gathering honeydew from jassids and membracids 
on the same plants, as well as nectar from the same extrafloral 
nectaries of Inga. Not only were the Crematogaster and Camponotus 
workers tolerant of each other in this potentially competitive situation, 
they were on quite intimate terms. They “greeted” each other with 
calm antennation on the trails, and on three occasions Wheeler 
observed Camponotus actually regurgitating to Crematogaster. 
It has not been established whether parabiosis is mutualistic or 
parasitic in nature. The distinction must be a subtle one in such a 
complicated relationship. The form <( parabiotica” of Crematogaster 
limata is evidently always associated with other ants. If future 
taxonomic studies prove it to be a species distinct from limata , it is a 
likely parasite. It would then be shown to be dependent on its associ- 
ates, while the latter species often nest and forage by themselves. But 
the prima facie case for mutualism seems even stronger. The broods 
are never mixed, and as Weber (1943) points out on the basis of his 
own studies, all of the parabiotic species participate vigorously to- 
gether in nest defense. There is no evidence that the presence of the 
Crematogaster harms the other species, except possibly by competition 
for the same food resources. On the contrary, Camponotus femoratus 
Manuscript received by the editor January 5, 1965. 
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