New ant species evolved within the nest of its relatives

A parasite queen (left) and the queen of the ants it preys on. Note the two scale bars both represent one millimeter, indicating the parasites' relatively small size.

University of Rochester

We tend to think of parasites as creatures that attach themselves to their hosts or worm their way inside, consuming the hosts' resources directly from their bodies. But there are other parasites that steal from their hosts simply by freeloading off them. The classic example is the cuckoo, which lays eggs in the nests of other birds, who then happily feed the cuckoo's offspring as if they were their own.

A successful strategy like that is hard for evolution to pass up. So it really wasn't a surprise to find out that there are also parasitic species of ants, ones that breed within the nests of other ants and raise their offspring using the resources provided by the hosts. Now, researchers have developed evidence that at least one of those species evolved within the nests that they now occupy.

The parasitic ant in question has the evocative name Mycocepurus castrator. It lives off the hard work of a related leaf-cutter ant named Mycocepurus goeldii. Although the host species is distributed widely within South America, M. castrator has a much narrower range—a single stand of eucalyptus trees conveniently located on the campus of Sao Paulo State University in Brazil.