New research shows butterflies use nectar to drug unsuspecting ants with mind-altering chemicals. The Japanese oakblue butterfly (Narathura japonica) enlists the help of ants (Pristomyrmex punctatus) to stand guard and protect its growing caterpillars (pictured) from predators such as wasps and spiders.
http://news.sciencemag.org/biology/2015/08/butterflies-drug-ants-turn-them-bodyguards