When plants are damaged, they emit a fragrance called green leaf volatiles, or G.L.V.’s. Most people have gotten a whiff of it — it is the smell of freshly cut grass.
But in the case of at least one type of wild tobacco plant found in the Great Basin desert of southwest Utah, it is an actual distress call. When the plant is attacked, the call triggers the arrival of bugs that act as little firefighters, according to a new study in the journal Science.
It works like this: when tobacco hornworm caterpillars start munching on the plant, their saliva interacts with the G.L.V.’s, causing a chemical change to the G.L.V. compounds.
This new compound attracts the arrival of insects known as true bugs that prey on hornworm eggs and larvae, thereby preventing further damage to the plant.
“It’s as if the caterpillar is calling the police on itself,” said Ian Baldwin, a molecular ecologist at the Max Planck Institute for Chemical Ecology in Germany and one of the study’s authors. “We wondered, how could this evolve this way?”
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