It seems like you find them everywhere, even in the animal kingdom. This freeloader inhabits in the Amazonas is a rather peculiar butterfly. It turns out that this species of butterfly simply picks up the bamboo secretions from ants and simply flies away with it. This relationship, known as kleptoparasitism, is the first ever documented between butterfly and ants.
Aaron Pomerantz, co-author of the study has said on thenextgenscientist.com, "They're kind of jerks at the adult stage. They're just stealing a resource, and they're getting away with it for now."
The species lives in South America, from Bolivia all the way to Guyana. In 2013, Pomerantz and his colleague Phil Torres were taking pictures of the butterfly in Peru, near the Tambopata Research Center. This is when they noticed that the butterflies were feeding on the bamboo sap where the ants lived.
They both realized that even when the species had been known for centuries, very little was known about them or their life cycle. So they started looking for the caterpillar, since, as stated by Pomerantz, "we had no idea what the caterpillars looked like; no one had ever seen them before."
After weeks of intensive looking, they finally found the larvae and their location. After coming several times to study them, they noticed that these usually stayed with the ants all through their life cycle, from larvae to adults.
At the beginning of the relationship, multiple ant species offer protection to the caterpillars while these provide the ants with amino acids and sugar through a specialized organ known as tentacle nectary organ. But then, when the butterfly becomes adult, they disguise themselves as ants to be able to easily take away the gooey sap without being disturbed.
It is still to be discovered why ants allow such thievery behavior. For now, the soundest theory could be that ants have poor eyesight and communicate themselves chemically through pheromones. So basically, they do not know what is going on.