Where do Butterflies go in the Winter
Butterflies spend the winter in one of two ways: a few species migrate to warmer regions, while the great majority stay put and pass the cold months in a dormant state called diapause, as an egg, a caterpillar, a chrysalis or, in a handful of species, an adult butterfly tucked into a tree hole, a log pile or a shed. Monarchs fly to Mexico and the California coast, but most of the butterflies you see in summer are still in your neighbourhood in January, hidden and not moving.
In this guide
- Do butterflies hibernate?
- Why winter is a problem for a butterfly
- Butterflies that migrate to warmer places
- Which life stage sits out the winter
- Where dormant butterflies hide
- How butterflies survive freezing
- When butterflies come back in spring
- How to help butterflies through the winter
- Did you know?
- Frequently asked questions
Do butterflies hibernate?
Yes, in the everyday sense of the word: most butterflies survive winter by going dormant, and only a few species escape it by migrating. Biologists prefer the term diapause to hibernation, because a mammal in hibernation is still burning fat to hold a low but regulated body temperature, whereas an insect in diapause has switched development off altogether; its body temperature simply follows the air, and its metabolism drops to a small fraction of the summer rate.
The other difference is timing. Diapause is programmed in advance: the shortening days of late summer, read by the caterpillar or pupa, trigger a hormonal change that stops growth and builds up fat and antifreeze compounds long before the first frost. A butterfly that merely stops moving on a cold night is in quiescence, a temporary chill that ends when the sun returns. Diapause needs a set number of weeks of cold before development can restart, which is why a warm week in January does not fill the garden with butterflies.
So the answer to where butterflies go is mostly nowhere. A meadow that held thousands of butterflies in July still holds their eggs, larvae and pupae in January, fastened to grass stems, curled inside dead leaves or hanging under bark. The lifespan of a butterfly depends heavily on which stage the species overwinters in: a dormant individual may live nine months while its summer relatives live three weeks.
Why winter is a problem for a butterfly
Butterflies are ectotherms: they take their body temperature from their surroundings rather than making it internally. To fly, the flight muscles need to reach roughly 28–35 °C, which is why a butterfly spends a cool morning basking with its wings angled to the sun, and why some species shiver their wings to warm up before take-off. In November, with the sun low and the air near freezing, no amount of basking gets a butterfly warm enough to fly, feed or escape a bird.
Cold is only half the problem. Winter also removes the food: nectar flowers die back, and the leaves that caterpillars depend on either fall or turn tough and low in nitrogen. The insect's solution is to stop needing anything at all for several months, and each family has settled on the life stage that does this best. The final danger is ice, because crystals forming inside a cell tear its membranes apart, so every butterfly that overwinters below zero must keep the water in its body from freezing.
Butterflies that migrate to warmer places
The famous exception to dormancy is the monarch. Monarchs east of the Rocky Mountains leave Canada and the northern United States in September and fly up to about 4,800 km to a dozen mountain groves of oyamel fir in central Mexico, at around 3,000 m above sea level. There they hang in clusters of millions from November until March, cool enough to stay dormant but rarely cold enough to freeze; the guide to butterflies in Mexico describes those reserves. Monarchs west of the Rockies make a shorter journey to eucalyptus, pine and cypress groves along the California coast.
Migrating monarchs are not simply avoiding cold; they are in reproductive diapause. The autumn generation emerges with undeveloped reproductive organs, stores fat instead of laying eggs, and lives six to nine months rather than a few weeks. Breeding resumes when the same butterflies fly north into Texas in March. The full circuit, explained in the guide to butterfly migration, takes three or four generations, and no individual ever makes the round trip.
The painted lady is the other great traveller. In Europe it moves between Africa and the Arctic Circle over several generations a year, and radar studies have shown the autumn flight south happening high overhead, out of sight, which is why people once assumed the butterflies simply died. In North America it recolonises the north from the southwestern deserts each spring. Red admirals, cloudless sulphurs and common buckeyes make shorter, looser southward movements, and their northern ranges are refilled by immigrants rather than survivors.
Which life stage sits out the winter
Every stage is used by some species, but the choice is fixed for each. In temperate regions the caterpillar is the commonest overwintering stage, followed by the chrysalis, then the egg, with dormant adults the rarest of the four.
Eggs
Many hairstreaks, coppers and blues lay in late summer and leave the egg on a twig or bud through the winter, with the fully formed first-instar caterpillar waiting inside. The purple hairstreak glues its eggs to oak buds in August and they hatch in April as the buds open. Overwintering eggs are among the most cold-hardy stages of all, because a tiny object with very little water is hard to freeze.
Caterpillar
Fritillaries typically hatch in autumn and hide in the leaf litter as first-instar larvae without eating, resuming on violets in spring. The viceroy rolls a leaf of willow or poplar into a silk-lined tube called a hibernaculum, fastens it to the twig so it cannot fall, and spends the winter inside as a part-grown caterpillar. Skippers overwinter in grass shelters tied with silk, and Europe's speckled wood is unusual in overwintering as either a larva or a pupa.
Chrysalis
The swallowtail family, the whites and the sulphurs mostly pass the winter as a chrysalis. A black swallowtail caterpillar that pupates in September forms a brown rather than green chrysalis, matching the dead stems it hangs from, and stays there until May. Cabbage whites, orange-tips and the spring azure do the same, which is why they are among the first butterflies of the year.
Adult butterfly
A handful of long-lived brush-footed butterflies overwinter as adults. In North America the mourning cloak, the commas, the question mark and Milbert's tortoiseshell do it; in Europe the small tortoiseshell, peacock, comma and brimstone. They emerge in late summer, feed heavily on rotting fruit and late flowers to build fat, and then hide; these are the butterflies on the wing in March while snow is still on the ground.
Where dormant butterflies hide
Overwintering butterflies choose places that are dark, sheltered from wind and rain, and cool enough to stay cold, because a hiding place that heats up on sunny days would wake the insect repeatedly and burn through its fat.
Adult butterflies use hollow trees, gaps behind loose bark, dense ivy, log piles, rock crevices and, very often, unheated sheds, garages, barns and attics. In Britain the peacock and small tortoiseshell are the classic winter visitors indoors, hanging with their wings closed so that the almost black undersides look like dead leaves. The mourning cloak in North America favours bark crevices and woodpiles.
Chrysalises hang from dead stems, fence rails, window sills and tree bark, usually a short distance from the host plant. Overwintering caterpillars are in leaf litter, grass tussocks and rolled leaves, and eggs are on the twigs and buds of the host plant itself. That is why the tidy autumn garden, with its cut stems and raked leaves, sends so many butterflies to the compost heap.
How butterflies survive freezing
A butterfly in diapause protects itself from ice inside the body, not on its surface. In late summer the insect empties its gut, reduces the water content of its tissues and loads its blood, the haemolymph, with cryoprotectants, chiefly glycerol together with sugars and sugar alcohols such as trehalose and sorbitol. These work like the antifreeze in a car radiator, lowering the temperature at which body fluids freeze, and they also stabilise cell membranes and proteins.
The result is supercooling: the body fluids stay liquid well below 0 °C. Many overwintering eggs, larvae and pupae can supercool to −20 °C or −25 °C as long as no ice crystal is present to start the freezing, which is why the empty gut matters, since food particles are perfect seeds for ice. A few insects go further and tolerate being frozen, confining ice to the spaces between cells; most adult overwinterers instead combine supercooling with a well-chosen shelter.
Snow helps: a caterpillar in leaf litter under 30 cm of snow sits close to 0 °C when the air above is −25 °C. Open winters with repeated thaws and freezes are harder on butterflies than steady cold, because every thaw wakes the insect and every freeze tests its antifreeze again.
When butterflies come back in spring
The order in which butterflies reappear follows the stage they overwintered in. Dormant adults are first, sometimes on a sunny day in late February in the southern United States or March in Britain, because they only need warmth to fly. Chrysalis overwinterers come next, from March to May, as soon as the pupa completes development. Egg and caterpillar overwinterers must hatch or resume feeding, grow and pupate first, so most fly from late May onwards, and the butterfly season builds gradually rather than arriving all at once.
Migrants arrive last and from the south. Monarchs leave Mexico in March and breed in Texas, and it is their children and grandchildren that reach Canada in June. Painted ladies reach northern Europe in May or June, and in invasion years such as 2009 and 2019 they arrive in tens of millions.
Diapause ends only after enough chilling followed by lengthening days and warmth, a safeguard against emerging in a mild spell in December. Unusually warm winters can still push emergence earlier, and a late frost can then kill adults that have already left their shelters.
How to help butterflies through the winter
The most useful thing a gardener can do is nothing. Leave dead stems standing until April, leave fallen leaves under hedges, and leave the ivy uncut, because each of these is somebody's winter quarters. Log piles, a rough corner of long grass and an untidy shed shelter overwintering adults, and a garden with the food plants of local species will have eggs and larvae hidden on them all winter.
A butterfly that appears indoors in winter has usually been woken by central heating, not by spring. Catch it gently in a box, let it settle in a cool dark place until it is still, then move it to an unheated shed, garage or porch where it can finish its dormancy and leave on its own in spring. Releasing it outdoors on a cold day is usually fatal, and a warm room will exhaust its fat within days.
On a larger scale, monarchs need their Mexican fir forests and Californian groves protected, since losing a winter site can erase a regional population in a single season.
Did you know?
- Butterflies that overwinter as adults typically live nine or ten months, the longest adult lifespan of any temperate butterfly.
- The first butterfly of the year in much of Europe is usually a brimstone, which may have spent the winter hanging in ivy disguised as a yellowing leaf.
- Every autumn the same groves in Mexico receive monarchs that have never been there before, guided by the sun and an internal compass rather than memory.
In summary
Butterflies go almost nowhere in winter. A few species, led by the monarch and the painted lady, migrate to warmer regions, but the great majority stay in their summer range and enter diapause as an egg, a caterpillar, a chrysalis or, in a few long-lived nymphalids, an adult hidden in a tree hole or shed. Antifreeze compounds such as glycerol let them supercool far below freezing, snow and leaf litter shield them from the worst cold, and the lengthening days of spring reverse the switch that shortening days threw in autumn.
Frequently asked questions about butterflies in winter
Where do butterflies go in the winter?
Most butterflies stay exactly where they lived in summer and pass the winter dormant, as an egg, caterpillar, chrysalis or adult, hidden in leaf litter, on stems, under bark or in sheds. Only a few species migrate; monarchs fly to central Mexico and coastal California, and painted ladies move south towards Africa and the deserts of the American southwest.
Do butterflies hibernate?
In everyday language yes, but the correct term is diapause. Unlike a hibernating mammal, a dormant butterfly does not regulate its body temperature at all; its development simply stops and its metabolism drops to a fraction of the summer rate. Diapause is triggered by shortening days in late summer and ends only after a period of winter chilling.
What do non-migratory butterflies do in the winter?
They enter diapause in whichever life stage their species uses. Fritillaries and viceroys overwinter as small caterpillars, swallowtails and whites as a chrysalis, hairstreaks and many blues as eggs, and a few long-lived nymphalids such as the mourning cloak, commas, tortoiseshells and peacock as adult butterflies hidden in tree holes, log piles and unheated buildings.
How do butterflies survive freezing temperatures?
By supercooling. Before winter a butterfly empties its gut, loses water and fills its body fluids with cryoprotectants, mainly glycerol plus sugars such as trehalose and sorbitol. These lower the freezing point so that the fluids stay liquid at −20 °C or below and no ice crystals form inside cells. Snow cover and sheltered hiding places keep the actual temperature far milder than the air.
Which butterflies overwinter as adults?
In North America the mourning cloak, eastern and other commas, the question mark, and Milbert's and California tortoiseshells. In Europe the small tortoiseshell, peacock, comma and brimstone, with the red admiral increasingly surviving mild winters. All of them emerge in late summer, feed to build fat and then hide until the first warm days of early spring.
In which life stage do most butterflies spend the winter?
As a caterpillar. Across temperate butterflies the larva is the most common overwintering stage, followed by the chrysalis, then the egg, and adult dormancy is the rarest. The choice is fixed for each species, so a black swallowtail always overwinters as a pupa and a great spangled fritillary always as a newly hatched larva.
Where can you find dormant butterflies in winter?
Adults hide in hollow trees, behind loose bark, in dense ivy, in log and rock piles, and in unheated sheds, garages, barns and attics. Chrysalises hang from dead stems, fences and window sills. Caterpillars are in leaf litter, grass tussocks and rolled leaves, and eggs are on the twigs and buds of the host plant.
Why is cold weather dangerous for butterflies?
Because butterflies cannot generate their own heat. Flight muscles need to be roughly 28–35 °C to work, so in cold weather a butterfly cannot fly, feed or escape predators, and ice forming inside its cells would kill it. Dormancy avoids all three problems by shutting the insect down until warmth and food return.
What should I do if I find a butterfly indoors in winter?
Move it somewhere cool and dark. Catch it gently in a box, let it become still, then put it in an unheated shed, garage or porch where it can go back to sleep and leave on its own in spring. Do not release it outside on a cold day and do not keep it in a heated room, which exhausts its fat reserves.
Do monarchs hibernate in Mexico?
Not in the strict sense, but they are in reproductive diapause. Monarchs cluster on oyamel firs at around 3,000 m in central Mexico from November to March, cool enough to remain mostly inactive and conserve fat, but they fly to drink on warm days. Their reproductive organs stay undeveloped until they head north in spring.
Published February 18, 2020 · Last updated September 21, 2026
Butterflies mentioned in this guide
Brush-Footed (Nymphalidae)Monarch (Danaus plexippus)Brush-Footed (Nymphalidae)Painted Lady (Vanessa cardui)
Brush-Footed (Nymphalidae)Mourning Cloak (Nymphalis antiopa)
Brush-Footed (Nymphalidae)Small Tortoiseshell (Aglais urticae)Brush-Footed (Nymphalidae)Viceroy (Limenitis archippus)Swallowtail (Papilionidae)Black Swallowtail (Papilio polyxenes)