The researchers used tiny pieces of cheese placed at the entrances of individual nests, initiating a string of thefts by ants that rippled from colony to colony.
Foraging ants generally took cheese pieces into their home nests within minutes, said Breed. Since thieving E. ruidum ants from different nests were usually lurking in the home nest, a tresspasser almost invariably took the cheese particle out of the home nest and into its own nest within minutes.
Interestingly, the same cheese bit was often observed being taken from the second nest by yet another larcenous ant, which took it to a third nest. At times, a single bit of cheese passed through a half-dozen nests in a relatively short period.
"There was a lot of cheese moving around these colonies," said Breed. "On the surface, it looks like counter-intuitive behavior with no simple explanation."
A paper on the 1998 work in Panama authored by Breed, CU graduate students Terrence McGlynn and Erin Stocker and 1998 CU graduate Anne Klein will appear in an upcoming issue of the international entomological journal, "Insectes Sociuax."
A 1992 study by Breed and several CU students in Costa Rica first confirmed the use of chemical camouflage by E. ruidum to enter neighboring ant colonies. The effectiveness of the chemical cues and their use as a camouflage was later replicated in subsequent laboratory experiments.
To test nestmate recognition by E. ruidum guard species in the 1998 Panama study, individual foraging ants from several colonies were captured, then chilled into a state of immobility. Individual chilled ants then were placed either on their own nest or on another nest entrance, said Breed.
In the majority of cases, the immobilized ants placed on the nests of
foreign colonies were dragged away from the nest entrance. However, at one site
furthest from the home nest, the guard ants rejected only eight of the
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Contact: Michael Breed
Michael.Breed@colorado.edu
303-492-7687
University of Colorado at Boulder
15-Mar-1999