The Miracle of Birth (and Metamorphosis)

A standard feature of many zoo butterfly gardens is the chrysalis box.  This is a window display in which cocoons are pinned up, with the idea that lucky visitors will be able to watch a butterfly emerge from the cocoon upon the completion of metamorphosis.  Once emerged, the butterflies are given some time to dry their wings before being released into the main enclosure.   Nor are the boxes limited to zoos - private gardeners who wish to release butterflies can obtain caterpillars or cocoons (much easier and more practical to transport than adult butterflies), watch them hatch, and then set them loose.

Likewise, some zoos place their incubators on display for their bird or reptile eggs.  Incubators for domestic chicken eggs use to be a much more common sight in farmyard and children zoo exhibits, though not as much anymore.  That's probably because butterfly gardens - with the quantity of animals needed and the short lifespan of their occupants - need constant replenishment of insects.  Chicken, on the other hand, can live for years and you only need a few, so hatching out constant chicks for display can quickly lead to a surplus problem.  The need for new chicks also is more seasonal, whereas butterfly exhibits - at least those indoors - need the new recruits year round.