Answer: Wasps

Many varieties of cotton, corn, and tobacco plants have an extremely sophisticated method of chemical defense. When under attack by caterpillars like the tobacco budworm and corn earworm, these plants release chemicals that signals nearby wasps, especially parasitic wasps, that they have a meal/host for the wasps.

These chemical systems are so sophisticated, in fact, that the plants can release blends of up to a dozen chemical compounds so that the wasps in the area know specifically what kind of pest is attacking the plant. Some wasps, for example, can only reproduce by using specific caterpillars as a host for their eggs, and the precise chemical signals used by the plants help guide those wasps to appropriate hosts. The wasps are able to feed and reproduce, and the plants are spared from an onslaught of hungry caterpillars.