How long does a caterpillar take to become a butterfly

To become a butterfly, a caterpillar first digests itself. But certain groups of cells survive, turning the soup into eyes, wings, antennae and other adult structures

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As children, many of us learn about the wondrous process by which a caterpillar morphs into a butterfly. The story usually begins with a very hungry caterpillar hatching from an egg. The caterpillar, or what is more scientifically termed a larva, stuffs itself with leaves, growing plumper and longer through a series of molts in which it sheds its skin. One day, the caterpillar stops eating, hangs upside down from a twig or leaf and spins itself a silky cocoon or molts into a shiny chrysalis. Within its protective casing, the caterpillar radically transforms its body, eventually emerging as a butterfly or moth.

But what does that radical transformation entail? How does a caterpillar rearrange itself into a butterfly? What happens inside a chrysalis or cocoon?

First, the caterpillar digests itself, releasing enzymes to dissolve all of its tissues. If you were to cut open a cocoon or chrysalis at just the right time, caterpillar soup would ooze out. But the contents of the pupa are not entirely an amorphous mess. Certain highly organized groups of cells known as imaginal discs survive the digestive process. Before hatching, when a caterpillar is still developing inside its egg, it grows an imaginal disc for each of the adult body parts it will need as a mature butterfly or moth—discs for its eyes, for its wings, its legs and so on. In some species, these imaginal discs remain dormant throughout the caterpillar's life; in other species, the discs begin to take the shape of adult body parts even before the caterpillar forms a chrysalis or cocoon. Some caterpillars walk around with tiny rudimentary wings tucked inside their bodies, though you would never know it by looking at them.

Once a caterpillar has disintegrated all of its tissues except for the imaginal discs, those discs use the protein-rich soup all around them to fuel the rapid cell division required to form the wings, antennae, legs, eyes, genitals and all the other features of an adult butterfly or moth. The imaginal disc for a fruit fly's wing, for example, might begin with only 50 cells and increase to more than 50,000 cells by the end of metamorphosis. Depending on the species, certain caterpillar muscles and sections of the nervous system are largely preserved in the adult butterfly. One study even suggests that moths remember what they learned in later stages of their lives as caterpillars.

Getting a look at this metamorphosis as it happens is difficult; disturbing a caterpillar inside its cocoon or chrysalis risks botching the transformation. But Michael Cook, who maintains a fantastic website about silkworms, has some incredible photos of a Tussah silkmoth (Antheraea penyi) that failed to spin a cocoon. You can see the delicate, translucent jade wings, antennae and legs of a pupa that has not yet matured into an adult moth—a glimpse of what usually remains concealed.

ABOUT THE AUTHOR(S)

Ferris Jabr is a contributing writer for Scientific American. He has also written for the New York Times Magazine, the New Yorker and Outside. Follow Ferris Jabr on Twitter Credit: Nick Higgins

You've probably seen monarch butterflies, and maybe monarch caterpillars, but there's a lot to learn about the monarch life cycle.

The monarch butterfly life cycle begins with a whirl of wings in the heat of the summer sun. As a female monarch sips nectar from a wildflower, a male hovers nearby. A pheromone is released from tiny black scent glands on his lower wings in hopes that she will accept his advances. He lingers until she perches on a leaf, a clear invitation. The two butterflies join together at the tips of their abdomens and stay that way for several hours until he is certain that no other male monarch will take his place. Several days later, the female is ready to lay eggs.

Monarch Life Cycle Stages

1. Egg
2. Larva (caterpillar)
3. Pupa (chrysalis)
4. Adult butterfly

Discover 7 fascinating monarch butterfly facts.

Milkweed leaves are the only things her future offspring will eat. She flits from leaf to leaf and uses special glands on her feet to “taste” each plant until she finds milkweed. Once she finds it, she lays eggs one at a time on the newest growth. Over the course of a week, the female lays several hundred white eggs, no bigger than a pinhead, on any milkweed leaf she finds.

Check out the ultimate guide to growing milkweed plants for monarchs.

Monarch Caterpillar

Four days later a minuscule caterpillar, also called the larva, emerges, already voraciously hungry. Its first meal is its own eggshell, and then it moves on to munch the milkweed leaves. The caterpillars exclusively eat milkweed. Try showy, common or swamp milkweed and butterfly weed.

Soon it outgrows its skin, which stretches but does not change size. The skin splits open and the caterpillar wiggles out, revealing new skin beneath. Over the next two weeks, it molts four times and becomes nearly 3 inches long.

Monarch caterpillars have distinctive white, yellow and black bands. One set of long, black filaments at either end are also a telling field mark.

Quiz: How many types of caterpillars can you identify?

Larva or Caterpillar?

Larva is the juvenile form of all insects that undergo a metamorphosis. Only butterflies, like these monarchs, and moths are called caterpillars during their larval stage.

Monarch Chrysalis

The caterpillar crawls away from the milkweed plant in search of a safe spot to begin the pupa stage of the monarch butterfly life cycle. It uses spinnerets near its mouth to create a tiny silken pad. Then it carefully hooks the tail end of its body into the pad and drops headfirst to hang in the shape of a “J.” A few hours later, the skin splits at the head one last time and falls away to reveal a green structure that hardens into a smooth, waxy shell flecked with gold. The making of the chrysalis is complete.

It takes 10 days to two weeks for a monarch to transform from a pupating caterpillar to an adult.

“I fell in love with monarchs when I found a chrysalis and watched this butterfly slowly emerge and fly away. The process made me think about the importance of learning to soar through changes,” says Carol Manglos-Foster of Onemo, Virginia.

Psst—monarch butterfly migration is simply magical. Use this monarch migration map to track the epic journey.

Adult Monarch Butterfly

Now the adult butterfly is nearly ready to emerge from the chrysalis. This is the last stage of the monarch butterfly life cycle. The outer skin thins and becomes transparent, exposing the colors of the wings and body that have formed inside. Next the chrysalis opens, and the butterfly crawls out headfirst. The wings are limp and its body is plump. It rests for a moment, then begins to pump fluid from its body into the wings. The wings expand and dry for a few hours, and then a breeze carries the butterfly off on its first flight.

“The metamorphosis monarchs go through to become adults is amazing. They rely on milkweed for survival, and with habitat disappearing, it’s more important than ever for gardeners to plant plenty of it,” says Jenny Miner of Irma, Wisconsin.

Are monarch butterflies endangered?

Attract More Monarchs

• Plant milkweed native to your area. Try growing several varieties. Ask your local extension office for their suggestions or learn more from the Xerces Society.
• Grow native, late-season nectar plants, such as goldenrod, aster and liatris, to provide migrating monarchs with the food they need.
• Avoid using pesticides, including any insecticidal soaps or oils.
• Add a shallow water source, flat warming stone and damp puddle for butterflies to lap up moisture and minerals. To create a damp puddle, fill a shallow container with sand. Sprinkle on a bit of sea salt or wood ash, and watch for the butterflies and bees to gather.

Next, check out the best monarch butterfly flowers you should grow.

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