Due to modification of brain dopamine signaling, the ants were just mad for the caterpillars. ~ Japanese ecologist Masaru Hojo
The Japanese Oakblue is a butterfly native to east Asia. Its caterpillars hire protection.
When ants encounter an Oakblue larva, they crawl over the caterpillar (as ants are wont to do to all sorts of things). This ambulatory encounter prompts an Oakblue caterpillar to secrete a sweet, sticky liquid that ants greedily lap up. The secretion addicts ants, enslaving them to the caterpillar. Within 3 days of first nipping Oakblue juice, an ant forsakes its responsibilities to the colony and devotes itself to the caterpillar.
Caterpillars are subject to attacks by spiders, parasitoid wasps, and other dangers. A caterpillar raises its tentacle organs near its rump as a ruse, to divert attacker attention toward its less-vulnerable rear. This rouses a doped ant, which grows aggressive when the caterpillar reacts to a perceived threat. Ants are formidable fighters; able to tackle predators that caterpillars can’t.