Ants Bathe Themselves to Win Wars

by Conor Lynch

Imagine a battalion of ants.  They fall into formation, identify their target, and then charge en masse. Much to their surprise, the warring ant colony defends this attack by dowsing them in acid, a miniature chemical warfare. How do they recover from such a devastating blow?

The answer resides in ant evolution.  The southern United States is slowly experiencing a change in the ant species that dominate it. Tawny crazy ants (Nylanderia fulva) and red imported fire ants (Solenopsis invicta) share a common history. They are both from areas of eastern and southern South America and they are battling over the same territory in the southern United States (LeBrun 1014).


Above: Tawny Crazy Ant
Below: Red Imported Fire Ant
(Images downloaded from Flickr)

This turf war has not gone unnoticed by scientists. Earlier this year Edward LeBrun, a postdoctoral fellow in the Fire Ant Project at the University of Texas, began a study of fire ant and tawny crazy ant warfare.  Known for their poisonous venom, fire ants typically dominate regions because other ant species typically avoid contact with fire ants because of this lethal venom. However, researchers at the Fire Ant Project were shocked to discover how easily the tawny crazy ants dominated the fire ants when the two colonies met in combat. Tawny crazy ants captured 93% of contested resources during the experiment when they were fighting with their rival fire ant colonies (LeBrun 1015)! Unlike other ants searching for resources, the tawny crazy ants will charge the fire ants despite the threat of venom.

This is because the tawny crazy ants have a secret weapon.  Once they come into contact with the venom, they undergo a process that appears to be biologically triggered. The contaminated ant stands up on its hind and middle legs and begins to groom itself, touching a gland that excretes different products to its jawbone. This gives the impression that the crazy ants are detoxifying themselves from the venom that the fire ants contain (LeBrun 1015). LeBrun and his team discovered that this grooming reaction was indeed a detoxifying ritual. To understand exactly how the detoxifying works, the scientists blocked the acidopore, which is responsible for formic acid production, and found a clear correlation between the grooming and survivorship. Blocking the acidopore allowed for the scientists to determine the role any secretions may have had in the detoxification. While the grooming didn’t lead to 100% survivorship, it was a clear improvement over the ants that had their acidopore blocked (LeBrun 1015). The mechanism behind the formic acid detoxification has yet to be unlocked, unfortunately.

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Graphs from the experiment detailing percent survivorship of ants in various scenarios relating to the venom

Scientists believe that this is a competitor specific evolution adaption; in other parts of the world tawny crazy ants fall victim to various ants that fire ants dominate with ease. So at some point in their history, these two ants have met and the tawny crazy ants developed an evolutionary expressed response that helps to ensure survival and can lead to the tawny crazy ants dominating fire ants when fighting over resources in the southern United States.

It is an amusing coincidence and an interesting scientific discovery that two invasive species sharing a common evolution history have again encountered each other on a different continent than their native one and that the developed genetic responses are still being expressed over time.

These results can have an effect on a wide variety of fields. It can help us to better understand natural selection and how it affects the survival of future generations. For example, my brother has an allergy to fire ant venom. When a fire ant bites him, the bite swells to an enormous size and he now has to carry an EpiPen in case of an extra severe reaction. A further understanding of how this detoxification reaction works could lead to new treatments for fire ant allergy sufferers.

Further study of these ant wars will also better help the scientific community to understand the dynamics of the ant world in the southern and southeastern United States. For years, fire ants have been wreaking havoc on their local ecosystems as they have become a dominant ant species in the southern United States (Pennisi 231).   In fact, Scientists now believe fire ants can impact electrical systems within houses (Maron 1).  Thankfully their move northwards is restricted by cold winter temperatures (Lockley 1). But now scientists are interested in how tawny ant’s defense tactics might affect the local ecosystems.

The dominance of the fire ant in the southern United States may be ending thanks to a trait that was selected for in crazy ants years ago. What long lasting effects will this have on ecosystems and humans alike in the years to come? We will just have to stay tuned to find out.

Further reading:
Ants and the art of War
Mercenary Ants Protect Farmers with Chemical Weapons
Slave Ant Rebellions

Works Cited

LeBrun, Edward. “Chemical Warfare Among Invaders: A Detoxification Interaction Facilitates an Ant Invasion.” Science 28 Feb. 2014: 1014-1017. Web. Full text.

Lockley, Timothy. “Imported Fire Ants.” Radcliffe’s IPM World Textbook. University of Minnesota, 4 Mar. 2013. Web. 17 Apr. 2014. <>.

Maron, Dina Fine. “The Rise of Crazy Ants.” Scientific American 13 Feb. 2014: Web. 17 Apr. 2014. <>.

Pennisi, Elizabeth . “When Fire Ants Move In, Others Leave.” Science 14 July 2000: 231. Web.