A yellow road-sign hanging from a tree warns "Butterfly Crossing," and the traffic is indeed intense. Dozens of yellow-and-black-striped zebras and classic monarch butterflies swoop, golden sulphurs hover high above, and orange julias flit about the garden that wraps around building contractor Ralph Johnson's Fort Lauderdale home. More than a year ago, Johnson and a friend, Bonnie Campbell, began courting butterflies. They sought books and seminars to find out which plants -- including cassia, milkweed, passion vine, and the wine-stained Dutchman's pipe -- attract the delicate creatures. Now Johnson and Campbell have their own photo album that tracks caterpillars through the pupa stage to full-blown butterflies and a log in which they've noted 13 species that have paid them a visit and as many as 70 sightings in the garden at one time. Johnson talks about putting together a guide to cultivating butterflies in South Florida and recently gave an impromptu instructional tour to a stranger who drove into his driveway and asked for his secret. He is already offering seedlings to his neighbors, sprinkling pollenlike fairy dust in the hope of creating a block-long private Butterfly World.