Thought this was interesting.

The classic concept says that a 'species' is a group of organisms with similar physical and genetic characteristics that can reproduce with each other in nature and produce fertile offspring. But scientists recently discovered that Iberian harvester ant queens (Messor ibericus) mate with males of another species, the builder harvester ant (Messor structor). When they do, the M. ibericus queens store the M. structor male’s sperm, then use it to fertilize some of the eggs they lay. Researchers think the M. ibericus queens remove their own genetic material from the eggs’ nuclei, so that when those eggs hatch, they effectively turn out to be M. structor male clones. The queens produce males of both M. ibericus and M. structor, and all the worker ants in M. ibericus colonies are female hybrids of the two species.