Honeybees protect plants from caterpillars by telling the pesky leaf eaters to buzz off, scientists from the Biozentrum University in Bavaria, Germany, discovered. Caterpillars are equipped with sensory hairs that enable them to detect air vibrations such as the sound of an approaching predator. Indeed a caterpillar’s life is not an easy one. Birds love caterpillars and so do carnivorous wasps. Several wasp species even use caterpillars as hosts for their young. Caterpillars therefore evolved features, such as the sensory hairs, to protect them from their enemies.
Jurgen Tautz and colleagues realized that these sensory hairs are not fine-tuned and caterpillars cannot distinguish between hunting wasps and harmless bees. If a flying object approaches, generating air vibrations in the proper range, caterpillars stop moving or drop from the plant. Fruiting trees, heavily laden with blossoms, get frequent visits from foraging honeybees. And caterpillars, stressed with the bees’ buzzing eat a lot less, Tautz explained.
The scientists conducted an experiment in which bell pepper plants were placed in tents with beet armyworm caterpillars and bees. They found that plants protected by buzzing bees suffered 60 to 70 percent less damage in their leaves. The discovery might have some practical application for sustainable agriculture. Surrounding crop plants with ornamentals sporting attractive flowers may help increase crop yield in areas infested with caterpillar pests.
The paper published in the recent issue of Current Biology is available at http://dx.doi.org/10.1016/j.cub.2008.10.038.