Gene-expression analysis showed infected ants' fat bodies resembled queens more than healthy workers, with changes tied to metabolism, immunity, stress and aging.
Brain data pointed the other way: infected ants had suppressed signaling molecules and receptors, a pattern that may underlie their loss of normal worker behavior.
The researchers said that weakens the idea that the tapeworm directly controls ants with its own peptides, instead suggesting it hijacks the host's regulatory networks indirectly.
That manipulation benefits the parasite's life cycle: pampered infected ants stay in the nest until woodpeckers eat them, allowing the tapeworm to mature in the bird's gut and spread via droppings.