Marta del Campo explains how the larvae of Manduca sexta, a moth nicknamed the tobacco hornworm, can become so chemically dependent on their favorite foods--the leaves of eggplant, potato, or tomato plants--that they would rather starve to death than eat leaves from other plants.

Tobacco hornworms raised on an artificial diet will eat any kind of plant material. Yet after only four or five days of feeding on a solanaceous plant such as tobacco, tomato, or hot pepper, they will refuse any other kind of plant food. Having become host specific, they will use taste organs located on hairs near their mouths to search out particular chemicals. In the absence of these chemicals, the caterpillars will not feed. If these hairs are removed, the caterpillars will once again return to feeding on any plant.

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