Queen ant makes males of another species for daughters to mate with

Bizarrely, Iberian harvester ant queens lay eggs that turn into male builder harvester ants, and some of her offspring are hybrids of the two species

By Tim Vernimmen

3 September 2025

Male ants of different species laid by the same mother: Messor ibericus (left) and Messor structor (right)

Jonathan Romiguier

Some of the eggs laid by Iberian harvester ant queens contain males of another species, the builder harvester ant – and these males father all of the workers in the colony.

“This statement sounds really, really crazy, like impossible,” says Jonathan Romiguier at the University of Montpellier in France. And yet, he discovered, it is true.

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The extraordinary ways species control their own evolutionary fate

Romiguier became intrigued by Iberian harvester ants (Messor ibericus) when he discovered that all the workers in M. ibericus nests were hybrids, with about half of their DNA matching that of the builder harvester ant (Messor structor).

The most likely explanation, it seemed, was that M. ibericus queens were mating with M. structor males. This kind of thing happens in some other ant species. No one knows why, but there are two competing explanations that appear to be most likely. One is that hybrids of closely related species benefit when the genes of each species compensate for some of the other’s flaws, a concept known as hybrid vigour.

Another possibility is that it might resolve a peculiar problem that M. ibericus shares with some other harvester ant species: whenever M. ibericus queens mate with M. ibericus males, all of their offspring become queens. This might be due to a genetic quirk that ensures its own inheritance but is devastating for the colony, which needs workers in order to survive. Breeding with another species may be a way to circumvent this.