Chemical warfare has taken on a whole new meaning with battles between ants producing a type of chemical that has been made artificially, but never previously observed in nature. 

The script sounds like something out of a horror movie of the Alien versus Predator variety. On one side are fire ants (Solenopsis invicta), whose nickname arises partly from their painful sting. The sting is an alkaloid venom, and while it is painful to us, it is deadly to most creatures their size.

However, Rasberry crazy ants (Nylanderia fulva) have a venom of their own, except this one is acidic, based on the formic acid so popular with ant species worldwide it may be affecting the atmosphere.

Unlike every other observed species however, the Rasberry ants appear to have studied high school chemistry, and know that acids and alkaloids (bases) neutralize each other. They've turned this on the fire ants, counteracting their venom to produce a viscous substance.

Previous research has shown that 98% of Rasberry crazy ants survive exposure to fire ant venom by grooming themselves with their own acid. When their venom glands were sealed, only 48% of crazy ants survived.

Now research published in Angewandte Chemie has identified the ammonium formate produced in the reaction as an ionic liquid.

Ionic liquids are salts in liquid form. You can liquefy sodium chloride by heating it to 800°C, and most other salts melt at similarly high temperatures. Ionic liquids are those salts that are liquid at moderate temperatures – definitions vary but below 100°C is a favored one. We use them in batteries, pharmaceuticals and plenty of other industrial processes. “The practical utility of ionic liquids makes the absence (heretofore) of reported examples from nature quite puzzling, given the facility with which nature produces many other types of exotic but utilitarian substances,” say the authors, led by Prof Li Chen of the Chinese Academy of Sciences Institute of Zoology.

Both species are native to South America, and it is thought the trait evolved there. Fire ants reached North America a while back, but venom neutralization was only noticed since the Rasberry crazy arrived in Texas around the turn of the century (the name comes from exterminator Tom Rasberry who drew attention to the invasion and the erratic way they move around).

Rasberry crazy ants have a much less painful sting than their enemies, but don't cheer them on too much – they have devastated the ecology of large areas of Colombia and often chew through electrical wiring. Their lack of interest in ant baits and habit of forming multiple-queen colonies makes them particularly hard to eradicate, but at least they've given us an idea for a fire-ant balm, not to mention high school chemistry demonstrations.

Hat Tip Popular Science