I planted milkweed in my garden back in the spring in hope of attracting monarch butterflies. They often lay their eggs on milkweed plants and the caterpillars eat the leaves. This fall, in addition to monarch caterpillars, we also had these nasty black and orange bugs (Son #1 calls them Assasin Bugs - I don't know if he's just making that up). Anyway, these black and orange bugs would eat the tiny monarch caterpillars.
My neighbor loaned me a couple of plastic and mesh bug houses and gave me instructions on "rescuing" the caterpillars. Yeah, yeah...I know: let nature take its course, the survival of the fittest, yada yada. But monarch butterflies are sooooo pretty.
As soon as the caterpillars were large enough not to crawl through the mesh of their "vacation home", we'd capture a few and put them inside. We'd add fresh milkweed leaves several times a day.
After they grew fat and happy, their appetites dropped off and they climbed to the ceiling of the house, attached themselves and hung in a "j" shape for a while. The caterpillar then formed its chrysalis (a process that took only a few minutes). After 10 to 14 days, viola! Butterflies!
We released them into my garden where I also have a lantana plant (mature butterflies like those, too.)