and watch the Metamorphosis process at work. All Caterpilar shipments should be next day air. Remember you must have willow for these caterpillars when they arrive. You may purchase your Willow from us at Shady Oak Butterfly Farm or from a local dealer. To Order Willow. Make sure the plant has not been sprayed with either an insecticide, or if grown Organically, is has not been sprayed with BT. Caterpillars usually take from one to three weeks to reach pupation size depending on species and temperature and size you ordered. For More information on Guarantee and Care