A Caterpillar Life Cycle Explained

a caterpillar life cycle

Caterpillars have evolved as “eating machines”, so their body grows quickly – sometimes doubling in size within days! At times their skins stretch to accommodate further expansion; once this point has been reached they must shed their old cuticles to continue growing.

Before a caterpillar pupates, it spins a silk pad from its last pair of prolegs. Some species also create a small hiding place called a chrysalis for protection during this process.


Egg phase: the egg stage of caterpillar life starts when eggs are laid onto milkweed plants and larvae emerge to feed on its leaves, buds, and stems for two weeks – during this time they go through five growing stages (known as instars) as quickly as four or five skin sheds per instar cycle – before hanging themselves up, spinning chrysalises to await metamorphosis into butterflies or moths.

A chrysalis is a protective silken casing that shelters caterpillars as they transform into butterflies and moths. Caterpillars that transform into butterflies often make chrysalises at the site where they fed as larvae; some species will form cocoons instead.

At this stage, caterpillars cease eating as they prepare to transform into adult butterflies or moths and need to conserve energy until then. When entering their chrysalis, caterpillars release digestive juices which break down most of their cells into “tissue cell soup,” creating four wings, new legs, eyes and mouthparts in the new butterfly or moth that emerges.

Once a caterpillar has emerged from its chrysalis, it may look very swollen and may wiggle its front legs back and forth or shake its body slightly. They will look for somewhere suitable to pupate; some species pupate attached to food plants while others dig into the ground or spin cocoons – the Monarch butterfly will often hang from a milkweed leaf when ready.

Once its chrysalis breaks open, a Monarch butterfly emerges, vulnerable and with wet wings crumpled together. Soon thereafter however, hemolymph – an insect blood-like fluid – will begin filling its wings, expanding them.

Though caterpillars’ vibrant colors and fuzzy exterior may make them endearing, they are formidable predators. To evade potential predators, caterpillars possess special glands which produce venom from their spines or fine hairs – this helps ward off birds, fish, toads and frogs, bats, snakes, ants and parasitic wasps as well as whistle to mimic bird calls to scare away potential predators and disarm pheromones signaling butterfly formation.


As soon as a caterpillar reaches its size limit for its skin, it becomes swollen. Neurohormones secreted by its body initiate molting; its old skin separates from its soft epidermis beneath in an effort to shed it quickly and fall to the ground where its siblings or parents can devour it. Unfortunately during molting periods predators become attracted by its ample supply of protein.

Once a caterpillar has shed its old skin, they begin to flourish again. A new head capsule develops and front legs lengthen. Their bands become more distinct while body bands branch more distinctly along its body surface. Furthermore, new breathing organs may arise which also act like claws for attaching leaves and drawing up water during their chrysalis stage.

Caterpillars may shed their skin five times during their larval stage. After reaching maximum growth, caterpillars seek out an ideal location for pupation; some prefer burrowing themselves into the ground while others form cocoons or spin silk mats around themselves before shed their skin again one last time before finally becoming chrysalises.

A caterpillar pupating into an amazing spectacle. Before making its silk pad and attaching itself, a caterpillar prepares its rear claspers into it before hanging upside down by its last pair of prolegs from it – hanging there for up to an hour while its chrysalis hardens.

As soon as it enters the chrysalis stage, caterpillars become vulnerable to predators once again. Their large bodies and vibrant hues make them easy targets for birds and insects hungry for sustenance. To protect itself, caterpillars form silky cocoons inside their black, brown or green chrysalis shell to form protective cocoons that eventually mature and enable their caterpillar to emerge into an adult butterfly or moth form. This process may take weeks to reach completion before this final transformation takes place and their first phase emerges into butterfly or moth form!


Once its larval phase has concluded, a caterpillar searches for a safe place to pupate – either leaving its food plant behind, burrowing into the earth, or spinning silk mats suspended from a hook-like apparatus called a cremaster at its tail end. When ready, they shed their last skin before creating a hard shell casing known as a chrysalis to transform their bodies into butterfly or moth wings through metamorphosis – an incredible transformation which takes place inside this protective casing while body parts transform themselves from caterpillar to butterfly or moth wings in this remarkable process known as metamorphosis.

Timely pupation depends upon species. Some caterpillars become ready to pupate within weeks after hatching from their eggs, while others will need overwintering before pupating in spring. Some caterpillars remain caterpillars for extended periods, including Cossus cossus’ Goat Moth which may remain dormant up to five years in a tree trunk!

At this stage, the caterpillar is safe from its enemies and predators while it stops eating to allow its body to prepare for metamorphosis. As digestive juices transform into “tissue cell soup”, their potential transformation into wings, legs, eyes, mouthparts, and genitalia begins.

As soon as a caterpillar is close to being transformed into a butterfly or moth, its cremaster pierces a silk pad. From there it hangs upside-down for days or more within its chrysalis until its transformation completes and it can emerge into the world.

After an exciting pupal period, butterflies or moths are ready to emerge from their chrysalises and fly off into a new life. After crawling out, splitting open its chrysalis, hanging themselves upside down to facilitate stretching and drying of newly formed wings (this may take two hours to fully dry), they can begin their new lives flying free from its protective cocoon.


Metamorphosis, or the change from larva to butterfly, involves four distinct stages – egg, larva, pupa and adult. At each of these points in time, cells within an insect undergo changes that allow it to adapt its form more readily for its new state.

A caterpillar’s life begins when she lays an egg, laid by a female. Once hatching, its tiny larvae (caterpillars) begin eating their way through a host plant; usually leaves, but sometimes stems roots flowers seeds fruit pods or pods too! Larvae are voracious feeders; their only goal in life is eating as much food as they possibly can!

As caterpillars enter their larva stage, they grow quickly – sometimes doubling in size within days! Their rapid development causes their skins to tighten with growth and require them to shed or molt in order to make room for continued development. Shedding and molting play an integral part in continuing development until reaching maximum length when they must seek out safe areas to shed once more and form an encasement called a chrysalis for protection from further threat.

Caterpillars are experts at creating chrysalises; these protective coverings are formed out of their own body tissues and often decorated with camouflaging colors or warning signs to deter predators. Some caterpillars even bury themselves underground to safeguard themselves against birds or other animals that might lay parasitic eggs inside during this vulnerable stage of their lives.

Once the caterpillar reaches its final molt, they stop eating and remain in their chrysalis for up to one week, depending on species and environmental conditions. At this stage they appear swollen and wrinkled before pumping fluid into their wings until they dry enough and become strong enough to support a butterfly when it emerges into adult form.

Once a caterpillar has completed its transformation into an adult, it will emerge from its chrysalis and fly away to begin its own life cycle all over again. This extraordinary transformation marks only the start of an incredible journey for this remarkable being.

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