The Basics About Butterflies
If you're new to butterflies, each butterfly has its own special plant (or group of plants) that it lays its eggs on. This is called a host plant. Host plants are plants that an organism lives on and lives off of. Some butterflies only have one host plant, some have a few. Without that host plant/plants, the butterfly is out of luck. They won't pick a different plant, they must have their host plant.
The Monarch & Milkweed Issue:
The host plant for monarchs is milkweed. It is literally the only thing they'll lay their eggs on. Milkweed grows primarily in fields and with suburban development, it gets wiped out. Most homes have a few bushes, a couple of trees and nothing else. No milkweed = No monarchs
Monarchs and other butterflies need host plants to lay their eggs and then for the caterpillars to eat (to munch on the leaves of the host plant), but as a butterfly, they can drink from any nectar source.
The Nectar Issue:
Now there's the issue of a food source: Nectar.
Nectar is what butterflies drink- and in case you're on Jeopardy - nectar is mainly a watery solution of the sugars fructose, glucose, and sucrose but also contains traces of proteins, salts, acids, and essential oils.
Here's the dirty little secret:
Not all flowers produce nectar! Crazy, right? Most folks assume that if it's a flower, it has what a butterfly needs, right? WRONG.
In our need for "pretty flowers", science has hybridized flowers (cross pollinated two varieties of flowers to get the prettiest traits). Groovy, but a lot of nutrition is lost and the end result could be a sterile (no nectar) flower!
In my research for this article, the internet is all over the place for what produces nectar, such as Asiatic lilies and daylilies. For the record, in my yard, I've never seen any butterfly (or bee) on a daylily or Asiatic lily. If they do provide something, it's of low nutritional value. Keep them if they make you happy, but make your life easy and add tried and true (native flowers) nectar sources if you're really trying to attract and feed butterflies.