Meet the phorid fly. Rather than take on the stresses of parenthood themselves, these flies use fire ants as a sort of sacrificial surrogate mother when reproducing. Here’s the basics.
The flies are attracted to fire ant colonies by the pheromones (basically smell-signals) that the ants use to navigate and communicate with one another. When the flies arrive, the ants give off even stronger “alarm” pheromones to alert the colony of the invasion, unaware that the pheromones are totally getting the flies even more hot and bothered.
The flies mate in mid-air, then the female, who is equipped with a “lock-and-key” ovipositor (egg-laying organ) like the one below, hovers over a potential “foster parent” until the perfect moment, when she swoops down, locks the ovipositor onto the ant, and injects a fertilized egg into the ant’s thorax.
From there, the larva hatches and then makes its way into the ants’s head, where it feeds off it’s body fluids for a few days during the fly’s pupa stage, while releasing a chemical that basically brainwashes the ant into acting normal (ant colonies naturally exclude ants that are acting strangely so as to avoid the spread of viruses), despite the obvious discomfort it experiences from being eaten from the inside out.
When the pupa decides it’s time to emerge, it uses this same chemical mind control to make the ant go to an area with a lot of leaf or plant litter where humidity levels are ideal for the fly. When the fly decides it’s in a good spot, it releases one last chemical which dissolves the ant’s remaining membranes, including the tissue that holds the head on, and emerges as an adult fly.
Here’s some sweet footage of the process: