I don’t know the species of either the butterfly or the ant in this video taken in Peru, but the interactions are complex.
One level is probable mutualism between the ants and the caterpillars. Although the authors don’t mention this for these species, there are a lot of caterpillar species that are guarded and protected by ant species. In these cases, the caterpillar, after nomming vegetation, secretes a sugary exudate that the ants feed on, and in return the ants keep the caterpillar safe from some predators. I suspect that’s what’s going on here; see the second video for such a case.
As for the adult butterfly “parasitizing” the ants, I’m not sure that’s what’s going on—unless the ants inadvertently signal to the adult butterflies that there’s nectar at the tip of the bamboo. Otherwise, it’s just competition for food. One puzzle is why the ants allow the butterfly to feed near them without driving them away.
While the butterfly wing patterns may mimic the ants, if that’s the case it may not be to fool the ants into accepting them (ants have lousy vision), but to fool predators who are wary of stinging ants. However, the mimicry is not that great. Another possibility is that the ants accept the adult butterflies because they’re going to lay eggs that produce the caterpillars that in turn exude that delicious nectar. And that would be a convoluted form of mutualism. It’s all very complicated, and I haven’t seen any papers on what’s shown in the video.
The notes from the YouTube video:
A walk through the woods in the Tambopata Amazon Rainforest can turn into a discovery of a never-before-seen behavior! Aaron Pomerantz (@nextgenscientist) and I (@phil_torres) collaborated on project to solve the mystery behind this incredible butterfly.
Here’s a short video on an ant/caterpillar mutualism, which also involves the evolution of auditory signals in the caterpillar. Remember, evolution is cleverer than you are.