Mycocepurus goeldii is a species of ant in the genus Mycocepurus.The species is parasitised by a closely related species, Mycocepurus castrator. The two diverged recently, around 37,000 years ago, and evolved in the same geographic region, making the parasite–host pair an example of sympatric speciation.M. castrator is directly descended from M. goeldii, its host. Such relationships are not uncommon among social parasites, as recognized by Emery's rule. Less common are cases like M.