One of the most remarkable characteristics of butterfly biology is that these insects undergo a process called complete metamorphosis. This is a fancy way of saying that adults lay eggs; the eggs hatch into larvae (called caterpillars); the caterpillars eat and ultimately pupate to form a chrysalis; and the pupa emerges as an adult to continue the life cycle. The primary advantage of this lifestyle is that it allows the caterpillars and adults to live in different places.
The caterpillar stage is very important - perhaps more important than the adult stage. The adult female lays an egg in the right spot on the right plant for the caterpillar. The caterpillar then eats, and eats, and eats until it pupates. From a gardener's point of view, you must know what plants caterpillars like to eat. By attracting the caterpillars, you will most surely get the adults that will feed on a variety of flowers. Caterpillar food plants should become your garden's foundation plants if you are serious about butterflies.
The following table lists food plants for common Kentucky butterflies.
| Butterfly | Subgroup | Caterpillar Food | Adult Food | Puddles |
| Monarch | milkweed | sap, fruit, nectar | ||
| Mourning cloak | birch, cottonwood, elm, hackberry | sap, fruit, nectar | Yes | |
| Painted ladies | American | sunflowers, pussytoes | nectar | Yes |
| Painted Lady | sunflowers | nectar | Yes | |
| Skippers | European | grasses | nectar | |
| Fiery | grasses | nectar | ||
| Silver Spotted | locust, woody legumes | fruit, nectar | Yes | |
| Swallowtails | Black | plants in carrot family | nectar | Yes |
| Zebra | hornbeam, paw paw, spicebush, tulip poplar | nectar | Yes | |
| Spicebush | spicebush, sassafras, tulip poplar | nectar | Yes | |
| Tiger | hornbean, paw paw, sassafras, spicebush, tulip poplar, wild cherry | nectar | Yes | |
| Tawny Emperor | hackberry sap | fruit, nectar | ||
| Viceroy | apple, cottonwood, plum, wild cherry, willow | sap, fruit, nectar | Yes |
