While the trees, shrubs and flowers in your garden are the main attraction, visiting birds and butterflies add an extra dimension so it makes sense to try and encourage them to come. Since most of the butterflies are native insects which are used to the native plants in the area, these natives are what you should include in your garden. This information comes from an article by Faith Peterson which I found on The Master Gardeners website.

The butterflies and moths that we see each day in summer are practically all native insects. That means that they have evolved, along with the plants that feed them, over centuries. You can help butterflies and moths by providing a suitable habitat of native plants in your yard that will allow them to grow and thrive.
A good butterfly habitat is ideally filled with native trees, shrubs and flowers. The nectar plants should be placed in a wind free sunny area, with a few rocks, from which butterflies absorb heat. Butterflies like mud puddles, and need a shallow water source. They also like rotted fruit, which should be placed in a shady area.
The life cycle of a butterfly is egg, caterpillar, chrysalis and butterfly. Each butterfly family has its favorite nectar plants; as well as its favorite (and only) sources of food for its babies (the caterpillars). Butterflies start as an egg laid by the female, who may lay eggs singly, or in clusters, usually on the underside of a leaf on a host plant. When the egg hatches it eats its shell and then starts eating the host plant leaves. As it grows it sheds its skin a few times. Stages between molts of the old skin are called instars; and they usually don?t look like the caterpillar until the final stage.

Caterpillars eat and eat and eat. When they have reached full size, they attach themselves to a firm support and become a pupa or chrysalis. When the metamorphosis is complete, the butterfly emerges, pumps blood into its proboscis to straighten it out; and into its wings to make them ready for flight. For many species, this all happens in one summer; and some actually have more than one generation per summer. Other species of moths and butterflies may over winter as eggs, or pupae and emerge the following spring. A brush pile in a corner of your property will provide a good protected location for over-wintering eggs and pupae.

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