A species of fungus-farming ants have given up sex altogether, reproducing asexually in female-only colonies.

A team of Texan and Brazilian researchers found that Mycocepurus smithii queen ants don’t need fertilization, and probably evolved beyond the need for males within the last 1 to 2 million years.

"Animals that are completely asexual are relatively rare, which makes this is a very interesting ant," says study author Christian Rabeling of The University of Texas at Austin.

"Asexual species don't mix their genes through recombination, so you expect harmful mutations to accumulate over time and for the species to go extinct more quickly than others. They don't generally persist for very long over evolutionary time."

No males of the M. smithii species have ever been found, and under a previous study the ants reproduced asexually under laboratory conditions, with researchers noting that no amount of stress induced the insects to produce males.

Rabeling dissected reproducing M.smithii queens from Brazil, finding that their sperm storage organs were empty.

The species is likely to be completely asexual across its entire range, which includes Northern Mexico through Central America to Brazil and some Caribbean islands.