Blue Sky Science: Why (and for how long) do butterflies stay in a cocoon?

Sophie Harrison


Why (and for how long) do butterflies stay in a cocoon?

Caterpillars start out as very small, tiny creatures. In the beginning they eat lots of food—just like the book “The Very Hungry Caterpillar”—and get bigger and bigger.

Eventually the caterpillar will be ready to transform into a butterfly or moth in a process called metamorphosis.

The caterpillar will go through the pupal phase which is where they form a cocoon or chrysalis. Butterflies make a chrysalis, while other insects—like the tobacco hornworm caterpillar—makes a cocoon and becomes a moth. They will stay and transform over time into a butterfly or a moth.

Most butterflies and moths stay inside of their chrysalis or cocoon for between five to 21 days. If they’re in really harsh places like deserts, some will stay in there for up to three years waiting for rain or good conditions. The environment needs to be ideal for them to come out, feed on plants and lay eggs.

The beautiful sphinx moths that come from the tobacco hornworm caterpillar will live for a couple of weeks to a month, depending on how good the conditions are. When they come out, they find a mate, lay eggs and start the whole cycle over again.