The life cycle of a butterfly has four stages: egg, caterpillar (larva), chrysalis (pupa) and adult. This is complete metamorphosis, in which the young insect looks and lives nothing like the adult. In warm weather the whole sequence from egg to butterfly takes about four to six weeks, but species that pass the winter in one of the stages can take a year. What is the life cycle of a butterfly? The four stages of a butterfly's life How long each stage lasts What happens inside the chrysalis Generations, broods and the winter stage Do all caterpillars become butterflies? How to watch the life cycle yourself Frequently asked questions What is the life cycle of a butterfly? The life cycle of a butterfly is the sequence of four stages every butterfly passes through: egg, caterpillar, chrysalis and adult. Each stage has a different body and a different job. The egg protects the embryo, the caterpillar eats and grows, the chrysalis rebuilds the body, and the adult flies, mates and lays the next generation of eggs. Biologists call this pattern complete metamorphosis, or holometabolous development. The word metamorphosis describes the transformation itself, the rebuilding of a crawling, leaf-chewing larva into a winged, nectar-drinking adult, while the life cycle is the whole loop from one egg to the next. Butterflies share this pattern with moths, beetles, bees, ants and flies; grasshoppers and true bugs instead hatch as miniature adults and grow by stages without a pupa. The cycle is remarkably fast. A monarch laid in June is an adult about a month later, and in warm regions several generations follow one another in a single year. The pace is set almost entirely by temperature and by the quality of the caterpillar's food, which is why the same species can take four weeks in Texas and eight in a cool northern spring. The four stages of a butterfly's life The cycle begins when a mated female finds the right host plant and glues a tiny egg to it, usually on the underside of a leaf. Most species lay singly, one egg to a leaf, and only a minority lay clusters. A butterfly egg is 1–3 mm across and may be round, barrel-shaped, spindle-shaped or flattened, often ribbed and beautifully sculptured under a lens. Inside, the embryo develops into a caterpillar within three to eight days in summer, and the shell darkens just before hatching. The guide to butterfly eggs describes how to find and recognise them. The larva chews its way out of the egg, often eats the shell as its first meal, and then does almost nothing but feed. Because its skin cannot stretch, the caterpillar grows in steps called instars, shedding its skin about four times as it passes through five of them, and its weight increases a thousandfold or more. This stage lasts two to five weeks in warm weather. The full-grown larva finally stops eating, empties its gut and wanders off to find a sheltered place to pupate. The caterpillar spins a small silk pad, hooks its tail into it and sheds its skin one last time to reveal the pupa, which butterflies call a chrysalis. Unlike most moths, butterflies make no cocoon; the chrysalis hangs or leans in the open, disguised as a leaf, a twig or a stone. Inside, the larval body is dismantled and the adult is assembled, a process covered in the guide to the butterfly pupa . In summer this takes one to two weeks; in species that overwinter as pupae it takes months. Adult butterfly The chrysalis splits along the back and the adult, or imago, crawls out with crumpled wings and a swollen body. It pumps blood into the wing veins to expand them, hangs still for an hour or two while they dry and harden, expels a drop of red waste called meconium, and then flies. From this point on it never grows again. Its work is to feed on nectar, find a mate and, if female, lay the eggs that start the cycle over. Most adults live two to four weeks, though the guide to how long butterflies live explains why a mourning cloak can survive for ten months. How long each stage lasts In warm weather the complete cycle from egg to adult takes roughly four to six weeks. The typical summer timings are: Caterpillar: 2–5 weeks, through four or five moults. Chrysalis: 7–14 days. Adult: 2–4 weeks for most species. Real examples show how much species differ. A monarch egg hatches in three to five days, the larva feeds for ten to fourteen days, the chrysalis lasts eight to fifteen days, and the summer adult lives two to five weeks, so a generation turns over in about a month. An eastern black swallowtail follows a similar summer timetable, but its last brood of the year stays in the chrysalis from autumn until the following spring, stretching that generation to six or seven months. A painted lady can complete the cycle in under a month, which is why it can breed its way across a continent in a single season. Temperature explains most of the variation. Insects are ectotherms, so a cool spell slows every stage: eggs laid in a cold May can take twice as long to hatch as eggs laid in July, and a caterpillar on tough, old foliage grows more slowly than one on fresh growth. Crowding and drought have the same effect. The older version of this page gave a fixed four to six days for hatching and one to two weeks for adult life; both figures are at the fast end of the real range rather than typical. What happens inside the chrysalis Metamorphosis is not a caterpillar growing wings. Inside the chrysalis most larval tissues are broken down by enzymes into a nutrient-rich fluid, while small clusters of cells called imaginal discs, present in the caterpillar since it hatched, multiply and build the adult organs from that fluid. Each disc has a fixed destiny: a pair for the wings, others for the legs, antennae, eyes and mouthparts. The caterpillar's chewing jaws are replaced by a coiled proboscis, the simple eyes by compound eyes, and the fleshy prolegs disappear entirely, leaving only the three pairs of true legs. Not everything is dissolved. The nervous system is reorganised rather than rebuilt, the breathing tubes are retained, and experiments have shown that moths and butterflies can remember odours they learned as caterpillars, so some neural connections survive the rebuild. The heart keeps beating throughout, and a chrysalis will twitch if touched, which is a defence against parasitoid wasps. Hormones control the timing. A juvenile hormone keeps the larva a larva at each moult; when its level drops in the final instar, the next surge of moulting hormone produces a pupa instead of a bigger caterpillar, and the surge after that produces the adult. The change is visible from outside in the last day or two, when the chrysalis wall turns transparent and the folded wings, already coloured, show through.

Generations, broods and the winter stage Because a generation can be completed in a month, most butterflies in warm regions produce several broods a year, while in cold climates many manage only one. Somewhere in the year the cycle must pause, and every species pauses at a fixed stage, a state of suspended development called diapause. Which stage is used varies by family. Many hairstreaks and coppers overwinter as eggs laid in late summer on twigs and buds. The viceroy , most fritillaries and many skippers overwinter as small caterpillars, often inside a rolled leaf. Swallowtails and the whites and sulphurs generally overwinter as chrysalises. A smaller group hibernates as adults: the mourning cloak, the commas and the tortoiseshells tuck themselves into hollow trees and woodpiles and can be flying on the first warm days of March, having lived ten months or more. Monarchs avoid the choice altogether by migrating to the mountains of central Mexico , where the same adults that left Canada in September lay eggs the following spring. The guide to where butterflies go in the winter lists the overwintering stage of each group. This is why the answer to "how long does the life cycle take" is either a month or a year, depending on whether a winter falls inside it. Do all caterpillars become butterflies? No. Every caterpillar becomes either a butterfly or a moth, and moths are far more numerous: of roughly 180,000 described species in the order Lepidoptera, fewer than 20,000 are butterflies. The larva of a moth is also called a caterpillar and goes through the same four stages, but most moths pupate inside a silk cocoon or underground rather than as a naked chrysalis, and their adults usually have feathery or tapered antennae rather than clubbed ones. Hornworms, woolly bears, armyworms and silkworms are all moth caterpillars. Nor does every butterfly caterpillar survive to become an adult. Eggs, larvae and pupae are eaten in enormous numbers by birds, wasps, ants and spiders, and parasitoid wasps and flies lay their eggs inside them. Only a small percentage of the hundreds of eggs a female lays ever complete the cycle; the guide to what eats butterflies covers the toll at each stage. That is the reason for the large egg counts described in the guide to how butterflies mate and reproduce . The pattern itself, however, is universal among the six butterfly families. A giant birdwing and a tiny blue, a swallowtail and a brush-footed butterfly , all pass through exactly the same four stages in the same order; only the timings, the host plants and the overwintering stage differ. How to watch the life cycle yourself The whole cycle can be followed in a garden or a jar. Find a female laying, or search the underside of host-plant leaves for eggs: milkweed for monarchs, parsley, dill and fennel for black swallowtails, nettles for red admirals and commas, thistles and mallows for the painted lady , cabbages and nasturtiums for whites. A leaf with an egg can be kept in a ventilated container with fresh food replaced daily; the caterpillar will hatch within a week, moult four times over the following weeks, and then hang from the lid to pupate. The chrysalis needs nothing but to be left alone and kept out of direct sun. When it darkens and the wing pattern shows through the shell, emergence is a day away and usually happens in the morning. Give the new adult a few hours to expand and dry its wings, then release it near flowers on a warm afternoon. Rearing a handful of caterpillars this way is the clearest lesson in insect biology there is, and it is also the surest way to identify a caterpillar whose species you are unsure of. A monarch caterpillar hatches at about 2 mm long and reaches about 5 cm in two weeks, an increase in weight of roughly two thousand times. Butterflies do not spin cocoons; a bare chrysalis is the mark of a butterfly, and a silk cocoon almost always means a moth. The adult that emerges is as large as it will ever be. A small butterfly is not a young one; it is a species that is small, or an individual that was underfed as a caterpillar. The wings, legs, antennae and eyes of the adult are already present as tiny discs of cells inside a newly hatched caterpillar. The last generation of monarchs each year lives about eight months, six to eight times longer than the summer generations, because it enters reproductive diapause for the migration. The life cycle of a butterfly is a complete metamorphosis through four stages: an egg laid on the host plant, a caterpillar that eats and moults through about five instars, a chrysalis inside which the larval body is rebuilt into the adult, and a winged adult that mates and lays the next generation. In summer the cycle takes four to six weeks; when a winter falls inside it, the species pauses as an egg, caterpillar, chrysalis or hibernating adult and the cycle takes a year. Frequently asked questions about the butterfly life cycle Egg, caterpillar (larva), chrysalis (pupa) and adult butterfly. The egg is laid on the caterpillar's host plant, the caterpillar eats and grows through about five instars, the chrysalis is the stage in which the larval body is rebuilt into the adult, and the adult flies, feeds on nectar, mates and lays the next generation of eggs. About four to six weeks from egg to adult in warm summer weather: three to eight days as an egg, two to five weeks as a caterpillar and one to two weeks as a chrysalis. Cool weather slows every stage, and species that spend the winter as an egg, caterpillar or chrysalis take up to a year to complete the cycle. Complete metamorphosis is development through four distinct stages, egg, larva, pupa and adult, in which the young insect looks and lives completely differently from the adult. Butterflies, moths, beetles, bees and flies all develop this way. Grasshoppers, dragonflies and true bugs undergo incomplete metamorphosis, hatching as small versions of the adult and growing without a pupal stage. Usually three to eight days in warm weather, with monarch eggs hatching in three to five days. The shell darkens as the caterpillar develops inside, and the larva chews its way out and often eats the empty shell. Eggs laid in late summer by hairstreaks and some coppers do not hatch until the following spring. Most of the caterpillar's tissues are dissolved by enzymes into a nutrient fluid, and clusters of cells called imaginal discs, present since hatching, multiply to build the wings, legs, antennae, compound eyes and proboscis of the adult from it. The nervous system is reorganised rather than destroyed, the heart keeps beating, and the wing pattern shows through the shell a day before emergence. About one to two weeks in summer for most species; a monarch spends eight to fifteen days as a chrysalis. Butterflies that overwinter as pupae, including most swallowtails and the whites, remain in the chrysalis from autumn until spring, which can be six months or more. Temperature controls the timing, so cool conditions extend it. No. Every caterpillar becomes either a butterfly or a moth, and roughly nine out of ten Lepidoptera species are moths. Moth caterpillars usually pupate inside a silk cocoon or in the soil, whereas butterfly caterpillars form a bare chrysalis. Many caterpillars of both kinds never reach adulthood because they are eaten by predators or killed by parasitoid wasps and flies. Most adult butterflies live two to four weeks, long enough to mate and lay eggs. Small blues may live only a week, while species that hibernate as adults, such as the mourning cloak, commas and tortoiseshells, survive eight to eleven months. The migratory generation of the monarch also lives about eight months because it delays reproduction until spring. It depends on the species, and each one uses a fixed stage. Many hairstreaks overwinter as eggs, viceroys and fritillaries as small caterpillars, swallowtails and whites as chrysalises, and mourning cloaks, commas and tortoiseshells as hibernating adults. Monarchs and painted ladies avoid winter by migrating to warmer regions instead of entering diapause. No. Once its wings have expanded and hardened, an adult butterfly never grows again, and a small butterfly is simply a small species or one that was underfed as a caterpillar. All growth happens in the larval stage, which is why a caterpillar eats almost continuously and increases its weight a thousandfold or more before pupating. Published February 20, 2020 · Last updated September 21, 2026