Instead, the host/parasite relationship appears to be built on mutual protection from a more fearsome foe, said Adams, an assistant professor of evolution, ecology and organismal biology.

The parasitic ants possess a volatile alkaloid-based venom that the host ants detect from a distance. The parasite ants’ potent chemical weaponry is known to work against a more-lethal invader ant.

“It’s likely a scenario where the enemy of your enemy is your friend,” she said.

To better understand the interplay between the ants, the researchers introduced the parasitic Megalomyrmex ant to Sericomyrmex host ants in a laboratory-controlled face-off.

“When confronted with a parasitic ant, the farmer ant will at first lunge at the intruder, but then instead of biting, she’ll pull away and bow her head down, in a submissive response.”

There are more than 250 species of these fungus-farming ants in the United States and in Central and South America, she said. The ants studied in this research live in Panama.

“These fungus farmers start little farms and care for the fungus garden by feeding it and protecting it from pathogens,” Adams said.

The crops are bountiful – more than what the host colony needs – so when the parasites invade it doesn’t cause a tremendous amount of stress to either the fungus or ants, she said.

And while they do eat some of the ants’ protein-rich brood, they don’t kill the queen and the host colony remains healthy.

Going forward, Adams hopes to discover whether or not this parasite-tolerance behavior is transmitted from parent to offspring colonies. Not all Sericomyrmex amabilis colonies live with parasites in their midst. Scientists estimate that about three-quarters of colonies host parasites.

“From an evolutionary standpoint, we’re interested in the ongoing relationships between hosts and parasites and what drives these seemingly unfair cohabitations,” Adams said.

“We now know that we need to not just consider hydrocarbons but consider other ant-derived chemicals that influence their behavior.”

Other researchers involved in this study were Alexandria DeMilto of Ohio State, Stefanie Neupert of the University of Konstanz in Germany and Falko Drijfhout and Simon Speller of Keele University in the United Kingdom.

The ant video above can be downloaded here. A video of Rachelle Adams explaining her work can be found here.