In arid regions use drought-tolerant butterfly flowers. Lantana, lavender, Sedum, verbena, and yarrow all thrive on dry, sunny sites. Create a shallow puddle to attract swallowtails, blues, sulfurs and other butterflies that enjoy drinking at mud puddles. A sprinkling of table salt and the addition of some manure will increase the puddle's appeal for butterflies. Salt harms plants, however, so use a plastic liner or locate the puddle away from your flower border.
Many pesticides kill indiscriminately so doom butterflies or their larvae.
Natural predators usually keep caterpillar populations under control. Also, the larvae of many butterflies feed only on certain plants and trees. Mostly, I welcome the occasional presence of butterfly caterpillars in my garden, sometimes carrying one indoors along with a spray of its food plant so that I can observe the miracle of metamorphosis. West Coast Ladies sometimes lay eggs on the leaves of ornamental mallows. Painted Ladies, which instinctively lay their eggs on thistle plants, also find an acceptable substitute in the hairy leaves of borage.