Biologists from the University of Vermont have discovered that ant queens fight to the death getting sperm from males of another species and use it to make sterile workers to build their colonies.

The research team observed the mating of two species of Pogonomyrmex harvester ants that are known for hybridizing along the border of Arizona and New Mexico. The cross-species copulation, however, is only used by the queens to make workers that would only build the colony of the queen that laid its egg, and not colonies of their own.

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To get the sperm of the other species, the queen ants trick the males into mating with them during the competitive mating season after the summer monsoon rains. The male ants can't tell apart one species from another prior to copulating. During the act, however, the true identity of the queen is discovered by the male ant.

To counter the strategy of the queens that lay sterile eggs, the males of the other species decrease the rate at which they deposit their sperm to the females.

"They can mate again," Sara Helms Cahan, the co-leader of the study and biologist at the UVM, said . She added that the act "would preserve their sperm for investment into better mating."

However, the queens have a counter-strategy to the counter-strategy of the males. The females have evolved to hold on to the males and don't let go.

"They lock slow males in copula significantly longer," says Helms Cahan, "until they eventually deliver the same amount of sperm that they normally would have. Essentially, they are sperm parasites."

The novel study on the ants, Helms Cahan said, is a "rather unusual R-rated example" of a bigger biological phenomenon dubbed the "Red Queen" hypothesis. Similar to the Red Queen in "Alice in Wonderland," who said, "you see, it takes all the running you can do, to keep you in the same place," the theory suggests that several plants and animals must continually adapt and evolve to not only gain a reproductive advantage, but also to avoid extinction when battling against rival, and also evolving, organisms in the endless shifting of life.

TagsAnt queen, Pogonomyrmex harvester ants, Arizona, New Mexico, Sperm, Cross-species breeding, evolution, Red Queen hypothesis