Like a larger African relative, the fly seems to lay its eggs in the heads of ants. The larvae then feed from the head’s muscle tissue; eventually the ant dies and its head falls off, whereupon the fly pupates and leaves the ant’s body.

Dr. Brown said the study was one more example of the importance of small creatures in the ecosystem. Insects in particular provide invaluable services like pollination and decomposition — and, in this case, ant control.

“People are so obsessed with dinosaurs and elephants,” he said, “they forget that the small things are out there.”