The tobacco hornworm, which feeds on tobacco plants, exhales some of the ingested nicotine to repel predators. Ian Baldwin and his colleagues at the Max Planck Institute for Chemical Ecology in Jena, Germany, glued tiny sensors to the mouths of tobacco hornworm larvae (Manduca sexta; pictured) to measure the levels of nicotine in their breath. They found that larvae that fed on engineered, nicotine-free tobacco plants (Nicotiana attenuata) exhaled less nicotine than larvae fed on normal plants, as did larvae in which an enzyme that transfers nicotine from the gut into the circulation was silenced. Wolf spiders (Camptocosa parallela) preferred to prey on larvae with less nicotine on their breath.
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