The pupal stage is an important one: while pupae do not require much direct care, they can have very specific demands which vary a lot depending on the species of butterfly/moth and their biology.
While a pupa may seem like a simple waiting game, there is much more to be considered. Temperature for example; some butterflies and moths from temperate regions overwinter as pupae. For overwintering, they will require a period of cold temperatures. If stored too warm they will outright refuse to emerge and die instead. The cold period of winter is a biological requirement for these pupae to emerge. This may be induced by storing them in your basement or refrigerator.
On the contrary, tropical species would most probably die or fail to emerge if stored in a cold environment, and require constant warmth and humidity to properly emerge. Their biology does not take cold into consideration, as most tropical areas have no pronounced seasons and are constantly very warm and humid.
Some species may not rely on temperature at all. African species for example will generally wait for a rainy season instead of a typical summer or winter. Their emergence may be triggered with a sudden increase in humidity after a period of drought.
As you can see, the needs of a pupa to emerge differ greatly per species, mostly depending on their origin and general biology. Temperature, humidity.. even light intensity and length plays a role in some species. It is greatly recommended to research the natural life cycle of a species when taking care of their pupae, and trying to recreate the conditions from their natural habitat.
Important is to store pupae in a slightly humid environment as pupae are very vulnerable to desiccation. They are unable to “absorb” moisture but a humid environment will prevent them from drying up. This applies to every species in general.
Up next, if you’ve done everything right is emergence, my favorite moment! Briefly after emerging butterflies and moths will have tiny, shriveled wings. The first thing it will do is climb or hang and find a secure spot to inflate the wings. Gravity aids them during this process, which is why they need to hang against a wall or in some cases upside-down. Some species have hanging pupae and they require to emerge “upside-down”: after emergence they will hang on to their empty pupal casing which provides them grip and a safe place to hang while pumping the wings. Many moths do the same and hang on to their cocoons. For example:
Generally pupae will emerge just fine when placed on the floor of a butterfly cage placed on a towel. Although there are exceptions, mainly Nymphalidae which require to hang upside down during emergence. The pupae can be suspended with a needle or glue.
While fairly straightforward, there are a few things to consider when dealing with pupating larvae. First of all, there are many different ways a caterpillar can pupate. Some spin a cocoon, some burrow themselves and pupate in a subterranean chamber, some spin a girdle and other larvae will pupate hanging upside down while attached to a silk pad. (Mainly Nymphalidae) Important is not to disturb or stress pupating larvae, this may result in failure and death. Subterranean pupators can be offered ar substrate in which they can burrow – like soil or paper towel.