I have several of the plants listed on the websites above and I can testify that the butterflies definitely come and they love the flowers. There are butterfly mix kits that have a mixture of flowers that butterflies love but these are only good if you want a wilder cottage looking garden. If a more ordered looking garden is what you desire then you might consider buying the seeds or plants individually so that you can place them more carefully. "This is a case of plant them and they will come."
Be aware that the host plants will end up with some caterpillars eating on them so they may have holes but be assured that these are baby butterflies in the making so don't harm the eggs, larvae, caterpillars or the chrysalis (butterfly mummies) which are all different stages of the butterflies. Usually the plants will be defoliated but not killed by the larvae and caterpillars. They will then grow back for the next crop of babies.
For an extra treat you can pour a regular sugared (not sugar free) Gatoraid in the sand to give them even more nutrients. Make sure it is not one of the energy drinks with caffeine or sugar substitutes in them.
Another great treat to offer the butterflies is fresh fruit. Place water in a shallow dish and put something to act as a pedestal in the water then set a plate of fruit on that pedestal to keep the ants away. Butterflies love all kinds of fruit especially overripe fruit. Some butterflies require the nutrients that overripe fruit offers. Some fruits that you can try are sliced oranges, apples, bananas, kiwi, strawberries, chunked watermelon, mango, pineapple, plums & berries, etc. Inspiration Green offers more really great tips for feeding butterflies with fruit (with pictures!).
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San Antonio Zoo