Caterpillar Setups > Semi-Closed Terrariums

High-humidity cages can spell doom for many species of caterpillars who live in a relatively dry environment and can get sick. The major exception to this are the admirals and viceroys. They are accustomed to feeding in humid riparian areas (especially in the eastern U.S.). Raising admirals and viceroys in a terrarium with a glass lid makes sense because the caterpillars do NOT get sick in this environment (of course, you still need to change out plant and remove frass once a week) and willows and cottonwoods stay succulent in the high humidity.