Every ant is a queen in this parasitic species — and they reproduce by cloning themselves and hijacking other ant colonies

A rare ant species in Japan has no males or workers ‪—‬ only queens, scientists have found. These ant queens live parasitically in the nests of another ant species and reproduce asexually to create clone queens to take over other nests.

The parasitic ant, Temnothorax kinomurai, is the "first known species with only queens," said Jürgen Heinze, a biologist at the University of Regensburg in Germany, and co-author of a new study describing the findings.

Most ants live in regimented, closely related societies in which queens retain sperm cells from when they mated before founding the colony. They use these sperm cells selectively to either lay fertilized eggs that will become female workers or queens, or unfertilized eggs that develop as short-lived males.

But there are also parasitic queens that infiltrate the colonies of other species and take them over, often getting the workers to serve them and rear their offspring until their own brood has taken over.

Keiko Hamaguchi, a biologist at the Kansai Research Center in Kyoto, Japan, and her colleagues have been investigating T. kinomurai, which has been found in only nine locations in Japan. The ant was suspected to operate differently and produce just queens without any workers or males, but it wasn't known for sure.

Young T. kinomurai queens invade the nests of a related species, Temnothorax makora, stinging the host queen and the most aggressive workers that try to stop the coup. If the takeover works, the surviving workers raise the alien queen's young.

"T. kinomurai needs the host workers for foraging and brood care and cannot produce offspring without them," Heinze told Live Science via email.

To work out what happens, Hamaguchi's team collected six colonies run by T. kinomurai queens and kept them in nest boxes in the lab. From these colonies, they reared 43 offspring, none of which were males, according to examination of the genitals, or workers, which would be smaller. All were queens.

When presented with new potential host T. makora colonies, seven of the 43 offspring, which had never mated, succeeded in coup attempts. This is in line with the typical high failure rate of the risky business of founding a parasitic colony. The seven queens produced a total of 57 offspring, which were also all queens. The findings were published Feb. 23 in the journal Current Biology.

Queens of some ant species can clone themselves through asexual reproduction, known as parthenogenesis. Other ants exploit social parasitism, hijacking the workforce of unrelated colonies to rear their own offspring.

"Yet, until now, no species had been shown to merge both strategies, despite the intuitive evolutionary logic behind such a combination," Jonathan Romiguier, an evolutionary biologist at the University of Montpellier in France who wasn't involved in the work, told Live Science via email.

"Given that there are over 15,000 ant species out there, this is quite unusual," added Daniel Kronauer, a biologist at The Rockefeller University in New York who wasn't involved in the study.

The benefits of sexual and asexual reproduction are normally finely balanced, he said. Asexual reproduction can allow an organism to maximize its own genetic contributions to the next generation by producing genetically identical daughters, and asexual species can often outcompete their sexual counterparts because they don't have to invest energy and resources into finding mates and producing males.

But sexual reproduction produces genetically diverse workers, which can be beneficial for an ant colony when it comes to pathogen defense and division of labor.

However, given that T. kinomurai queens don't produce workers anymore, those benefits have disappeared, Kronauer told Live Science. "This could shift the balance in favor of asexual reproduction and, ultimately, the loss of males," he said.