Here is a potted plant of fennel (Foeniculum vulgare) which serves as a great lab host of many machaon group swallowtails.  The potted plants are in an open terrarium; but, to keep the plant and caterpillars from cooking, I have placed a screen top to allow for airflow.  In this photo, the larvae feeding on the fennel are desert swallowtails (Papilio coloro.)