Sweet Treat Leads To Stinky Predation

When a moth caterpillar munches on the tasty leaf hairs of tobacco plants, the meal delivers the herbivore an indirect death blow: Modified sugars attached to the leaf hair get chopped off by esterases in the caterpillar’s digestive tract. The resulting sugary poop smells distinctly of baby vomit to humans but like Sunday dinner to the caterpillar’s predator, an ant called Pogonomyrmex rugosus. After the aroma of these O-acylated sugars draws the ant to the caterpillar, the ant then carries its meal home to the nest so that the whole family can feast (Proc. Natl. Acad. Sci. USA, DOI: 10.1073/pnas.1101306108). Consuming the sugars “has a similar effect for larvae as the consumption of asparagus has for humans,” in that it makes one’s excretions stink, explain researchers Alexander Weinhold and Ian Thomas Baldwin of the Max Planck Institute for Chemical Ecology, in Jena, Germany. Although only a potential social annoyance for humans, these smelly emissions can have “more serious consequences for a caterpillar,” they note. Next up, the team is figuring out whether the tobacco plant evolved the sugars to intentionally kill the caterpillar or whether the ant simply evolved its sense of smell to detect the aroma.