Place cuttings of snow brush in bottled water.  Cork the opening with toilet or facial tissue; so that the plant goes through to the water; but caterpillars cant'.   Replace host every five days or so or when caterpillars have depleted cuttings.  Make sure your lid either has holes or cut a hole out of the lid and place screen over the hole so that caterpillar frass will dry and not get your larva sick.