and watch the Metamorphosis process at work. All Caterpillar shipments must be next day air. Remember you must have Fennel or other of their host plants for these caterpillars when they arrive. You may purchase your Fennel from us at Shady Oak Butterfly Farm or from a local dealer. To Order Fennel. 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