A case of parabiosis between two Attini

In the Online First of Insectes Sociaux is an article on a common nest between a Cyphomyrmex and an Apterostigma. If the fact that they share the nest is not finally that much surprising, what I found was is the way the fungus garden is made. Here is the abstract:

Parabiosis between basal fungus-growing ants (Formicidae, Attini)
C. E. D. Sanhudo, T. J. Izzo and C. R. F. Brandão

Abstract. We describe the first observation of parabiosis between two Attini ants (Apterostigma urichii Forel and Cyphomyrmex faunulus Wheeler) found in northern Manaus, AM, Brazil. Complete, mature colonies of both species were found in a single cavity inside a rotten log, sharing and tending a single combined fungus garden, made up of two distinct halves, each cultivated by one species. Workers of one species often antennated workers of the other species and showed no aggression toward each other or toward each other’s workers, queens, or immatures. Laboratory observations suggest that immatures of both species feed on hyphae from either half of the fungus garden. We were not able to find other parabiotic pairs involving the same species in the same locality, although we found colonies of both species sharing trails and foraging territories.