Caterpillars, the larval stage of butterflies and moths, primarily eat and grow to fuel their transformation into winged adults. Their diet is crucial for development.
The Primary Diet of Caterpillars
Most caterpillars primarily consume leaves, which provide the nutrients for their rapid growth. Specialized chewing mouthparts (mandibles) efficiently process tough plant material, aided by a long intestine designed for digestion.
Caterpillars have large appetites, often eating continuously day and night. This relentless feeding allows them to store energy reserves for metamorphosis. Some species consume many times their own body weight in plant material. Fresh leaves also provide necessary moisture, as caterpillars typically do not drink water directly.
The Specificity of Host Plants
While most caterpillars eat leaves, many species require specific “host plants.” This specificity results from co-evolutionary relationships, where caterpillars adapt to overcome plant defenses. If a caterpillar does not consume its specific host plant, it may not develop properly or could even starve.
A well-known example is the Monarch caterpillar, which feeds exclusively on milkweed plants (Asclepias species). Without milkweed, Monarch larvae cannot complete their development into butterflies. Similarly, Black Swallowtail caterpillars feed on plants in the carrot family, such as parsley, dill, and fennel. Other examples include Eastern Tiger Swallowtails, which use trees like tulip tree, black cherry, and sassafras as host plants.
Beyond Common Leaf Diets
While most caterpillars are herbivores, some species have evolved more specialized diets. They may consume other plant parts like flowers, fruits, seeds, or roots. Budworms, for example, bore into and eat plant buds and flowers. Fruit-eating caterpillars, like the codling moth larva, bore into apples and pears, while pea moth larvae feed inside pea pods.
A small number of caterpillar species are carnivorous, preying on other insects. Hawaiian Eupithecia moths, for example, actively hunt and consume insects like fruit flies, using specialized adaptations. Some species, such as the harvester butterfly caterpillar, feed on aphids. Other rare instances include caterpillars that consume detritus or scavenge dead insects.
What to Avoid Feeding Caterpillars
If you find a caterpillar, providing the correct food is paramount. The wrong plant can be harmful or fatal, as their digestive systems are highly specialized for specific host plants. Caterpillars derive all necessary moisture from their food, so they do not require a separate water source.
Avoid feeding caterpillars leaves from pesticide-treated plants. Systemic pesticides can make the plant toxic, leading to illness or death. If a plant’s origin or treatment history is unknown, avoid feeding it to caterpillars. The safest approach is to feed a caterpillar leaves from the exact plant on which it was found.