Butterflies can seem friendly and harmless. But at least one type has learned to raise its young as parasites, tricking ants into feeding it and giving special treatment.
The pupae of the European butterfly Maculina rebeli exude a scent that mimics the ants and make themselves at home inside the ant nest. Once they become a caterpillar they even beg for food like ant larvae, researchers report in Friday's edition of the journal Science.
But, not content just to be fed, the butterflies even manage to demand special treatment, Jeremy A. Thomas of Britain's University of Oxford and colleagues report.
It turns out that ant queens make subtle sounds that signal their special status to worker ants. The caterpillars have learned to mimic those sounds, the researchers say, earning high enough status to be rescued before others if the nest is disturbed.
In times of food shortage, nurse ants have been known to kill their own larvae and feed them to the caterpillars pretending to be queen ants, they added.
In nature, the real ant queen and the caterpillar keep to different parts of the ant colony and would not encounter one another, the report said.
But in an experiment, a butterfly pupa pretending to be an ant queen was placed in a chamber with worker ants and four real ant queens. The ant queens began to attack and bite the caterpillar, but the workers intervened, biting and stinging their own queens, which they then pulled to a far corner of the chamber while other workers attended the pupa.