Plants that give off an airborne "SOS" when being eaten by bugs may just be attracting more diners.
A team of scientists from Switzerland found an odor released by maize plants getting eaten brought in parasitic wasps and Egyptian cotton leafworm moth caterpillars, according to a Frontiers press release.
Plants often release volatile organic compounds when damaged; these are similar to substances that cause the smell of freshly cut grass.
The plants release the compounds in an effort to attract insects that prey on herbivores munching herbivores. The smell attracts parasitoid wasps, which lay eggs in other insects.
"Adult moths and butterflies avoid food plants that are under attack by conspecifics. This seems adaptive, because it reduces both competition and the risk of predation by parasitoids. But we found that [Spodoptera] littoralis caterpillars are actually attracted to the odor of damaged maize plants, even when this odor is mimicked in the laboratory with a mix of synthetic compounds," said Prof. Ted Turlings, an head of the Laboratory for Fundamental and Applied Research in Chemical Ecology Institute of Biology at the University of Neuchâtel, Switzerland who participated in the study.
The scientists put the Spodoptera littoralis caterpillars in an olfactometer to see what scents they were most attracted to.
The caterpillars were over twice as likely to go towards recently damage maize plants than any other scent or plant.
Researchers believe the caterpillars choose these "in distress" plants because they are easier to locate. Little caterpillars fall off of plants and into the soil, making them extremely vulnerable to predators and pathogens. The compounds given off by the plants can help the moth larvae get out of the dirt faster.
"The caterpillars feed less and move more when exposed to high concentrations of the volatiles. By moving away from freshly damaged sites, they can minimize risk of predation and avoid competition," said Prof. Turling.
