Complete Metamorphosis

Complete Metamorphosis

Photograph by Daniel Shea


words by willow defebaugh

The Overview examines a previously explored phenomenon in new light: the one by which a caterpillar becomes a butterfly.

“Cut a chrysalis open, and you will find a rotting caterpillar. What you will never find is that mythical creature, half caterpillar, half butterfly, a fit emblem of the human soul, for those whose cast of mind leads them to seek such emblems. No, the process of transformation consists almost entirely of decay.”

Pat Barker

Few creatures embody transformation quite like those who exhibit complete metamorphosis. Roughly 800,000 species of insects undergo this form of development, equating to 85% of all insects and 70% of all known animal species. It involves a life lived in four stages: egg, larva, pupa, and imago (adult). As ubiquitous as this process is, there is one animal we associate with it above all others: the butterfly, which shares almost no physical traits with its earliest form save for dormant groups of cells called imaginal discs.


After hatching from an egg, a caterpillar (the larva stage) starts to feed. It inches up trees and stalks, feeding mostly on plant matter. It does so until its tough skin becomes too constrictive and a hormone is released that triggers it to shed its outermost layer. This process repeats around four times as the caterpillar continues to nourish itself and grow larger over the two to five weeks it spends in this stage. While we tend to focus on the stunning shift from larva to imago, these smaller sheddings that precede it are equally essential to the butterfly’s eventual emergence.


Up until this point, the caterpillar’s imaginal discs have been suppressed by a juvenile hormone, the levels of which only drop when it has fed enough. Once this occurs, the caterpillar enters a period of stillness. It stops eating and moving. A final flooding of hormones causes another layer of skin called the pupal cuticle to form beneath its surface as its outer skin is sloughed off yet again, leaving behind what many of us might recognize as its pupa form: the chrysalis.


Inside, that same hormone surge has also sent out a signal for the caterpillar’s cells to self-destruct, liquifying all of its muscles, fats, and other matter that made up its previous self. All that is spared are some vital tissues including parts of its respiratory system, heart, mushroom-shaped brain, and those imaginal discs now stirred to action. The liquified goo of the caterpillar then fuels the growth of eyes, antenna, legs, genitalia, and wings from these discs. From this state of total dissolution, a new being begins to form


A butterfly may stay in its chrysalis anywhere from 10-14 days, a reminder that transformation takes time. Because temperature is a factor in determining when it’s time to enter its final stage, in harsh climates, some species may even wait for years for the right conditions. Chrysalises not only provide the conditions for transfiguration, they also protect what’s inside when its environment is not ideal, and help efficiently pass weeks when resources might be scarce. When the time does finally arrive, one last shedding of the pupal cuticle and the butterfly emerges.


Once outside its casing, the adult butterfly must allow for its wings to unfold by hanging upside down as a liquid pumps through their veins causing them to take shape and solidify. If rushed, the imago will never be able to fly. Adult life spans vary, but the average is only two to four months—meaning some butterflies spend as much or more time becoming themselves than they do the end result. Despite this dramatic display of change, perhaps more poetic yet is that imagos retain traces of who they once were: memories and learnings from their lives as caterpillars, never forgetting what it takes to transform. 


Complete metamorphosis is both gory and glorious. If it feels familiar to you, you’re not alone; there is a reason we are so fascinated with butterflies. At so many scales, their story is our story. We grow and shed our skin. At times, we feel as if we have been liquified entirely. We harden and isolate ourselves. Just when we think we have lost it all, everything we were, something new emerges. And while the caterpillar might not be able to imagine all it will one day turn into, deep down those parts have always been inside—blueprints for what it was meant to become.

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