How to Rear Butterflies at Home: A Beginner's Guide for Enthusiasts, Insect Lovers, Families and Schools

Most people think rearing butterflies is something you need a greenhouse, a garden, and a lot of experience for. It is not. You need a net, a mesh cage, a jar of cut plants, and a window sill. One afternoon in a meadow gets you started, and a few weeks later you are watching adults come out of their pupae on your kitchen table.

It is also the best nature lesson I know of, and not only for children. Whether you are a collector who wants perfect specimens without hunting for them, someone who simply likes insects, a parent looking for a project that beats a screen, or a teacher who needs something a class will remember, you get the same thing out of it: the entire life cycle in front of you, live, at a speed you can actually follow. And at the end you carry the adults back to the same meadow and let them go, which is the part everybody remembers.

Why rear them at all

In the wild, only a few percent of eggs make it all the way to an adult butterfly. The rest get eaten, parasitized, or dried out. A single female can lay several hundred eggs, sometimes over a thousand.

Take a brood into a cage and you multiply that survival rate several times over. So when you let them go, you are not taking anything from the meadow. You are handing it back far more adults than it would have produced on its own.

And because the female came from that meadow, everything you release belongs there. Same species, same local population, same genetics. There is no risk of putting an alien species or a foreign genetic race into a habitat, which is exactly the risk you run with butterflies bought from somewhere else. Catch locally, release locally, and the whole thing is a straight gain for the local fauna.

It is easier than it looks, and you do not need a garden

You do not need plants growing in soil. Cut stems standing in a jar of water work perfectly well for the entire rearing.

There is one thing you have to get right, and it catches almost everybody the first time. Plug the neck of the jar with cotton wool. If the caterpillars can reach the water, they fall in and drown. A wad of cotton around the stems closes the gap completely and still lets you top the water up. That single detail is the difference between a rearing that works and one you lose overnight.

Keep a supply going by collecting a larger batch at once, washing it, shaking the water off, and storing it in a plastic bag in the fridge. Dry it slightly before you feed it out.

Start with a common species

The commonest butterflies are the easiest to rear, which is lucky, because they are also the ones you will actually find.

In Europe, that means the clouded yellows (Colias), the whites (Pieris and Pontia), the marbled whites (Melanargia), the walls (Lasiommata), the meadow browns (Maniola) and the blues (Polyommatus). In North America the same logic applies to the local whites and sulphurs and to the satyrs and wood nymphs. These are abundant, they are not fussy, their foodplants are ordinary meadow plants, and losing a few caterpillars to a beginner mistake costs the population nothing.

Rare species are a different discipline. Leave them until you have a few broods behind you.

The nettle butterflies, and the shortcut nobody tells beginners about

If I had to point one group out, it would be the nymphalids that breed on stinging nettle. They are easy to rear, they lay readily in a cage, and in Europe they are everywhere: the peacock (Inachis io), painted lady (Vanessa cardui), red admiral (Vanessa atalanta), map butterfly (Araschnia levana) and small tortoiseshell (Aglais urticae).

And there is a shortcut. You do not have to catch a female at all. These species lay in batches, so their caterpillars live in big communal nests on nettle, spun into the tips of the plants. Find one and you have fifty to a hundred caterpillars in a single patch, already hatched and already feeding.

That is the fastest possible start. You skip the catching, the laying, the waiting and the egg stage, and you go straight to the part children actually want to see. Take a portion of the nest, not the whole thing, put them on fresh nettle in a cage, and you are rearing butterflies the same afternoon. Nettle grows on every field edge and waste corner in Europe, so the food problem solves itself too.

Identify it first, then read up on it

This is the step beginners skip, and it is the one that decides whether the rearing works.

Before you set anything up, know what you have caught. Then look the species up and find out two things:

• What the caterpillars eat. No foodplant, no rearing. This is not negotiable and it is species-specific.
• How many generations it has per year, and which stage overwinters. This tells you whether you are running a brood through in a few weeks or settling in for the winter.

Ten minutes of reading before you start saves the whole project. Going the other way around, with a cage full of caterpillars and no idea what to put in it, does not end well.

Check what is protected before you catch anything

Rules differ from country to country and sometimes from region to region. Some species are protected and may not be collected at all, and some sites are off limits regardless of what is flying there. Look up your local regulations before you go, and if you are not sure what you are looking at, do not catch it.

Catching a female

Everything starts with catching the right insect.

Most butterflies show some sexual dimorphism, and in many species the sexes differ enough in shape and color that a beginner takes them for two species. Where that does not help, check three things:

• The abdomen. Females have a noticeably larger, fuller one.
• The outer margin of the forewing. Usually more rounded in females.
• The antennae. In groups where males have broad feathered antennae, feathered means male.

For a female you intend to breed from, condition does not matter at all. Worn, faded, slightly damaged, she lays exactly the same eggs. Only keep the specimens you genuinely want for a collection, and let everything else go.

A workable net has a ring 30 to 40 cm across and a bag about twice as deep as the ring is wide, so the butterfly cannot simply fly back out. A handle up to 1.5 m gets you to insects in awkward places, and a telescopic pole you can adjust in the field is better still.

Do not swing hard. Violent movements damage the butterfly inside the net. Swing, then flip the loose end of the bag back over the rim of the ring. That one motion is what keeps it in there while you walk up.

Picking her up without wrecking her wings

There is exactly one place to take hold of a butterfly: the leading edge of the forewings, the front margin, with the wings closed together over her back.

That edge is the stiff, reinforced part of the wing. Held there, nothing bends and nothing rubs off, so you do not damage the wings at all. It is a safe grip and it is the only one worth learning. Grip her across the middle of the wing instead and you strip scales off in a single touch; grip the body and you crush her.

Getting her home alive

Never use a killing jar for a female you intend to breed from. What I use instead is a glassine envelope, with the envelopes packed into a small rigid plastic box.

Slide her into the envelope with her wings closed and fold the flap over. It sounds rough and it is the opposite: in the dark, with her wings held closed against each other, she is in a safe position and physically cannot damage herself. She stops beating, sits still, and arrives with her wings intact. The plastic box then stops anything from crushing the envelopes in your bag.

The one thing that will kill her is heat. Put the box somewhere it cannot cook: a backpack, a hip pack, or in a car, the trunk or the floor under a seat. Never on the rear shelf under the back window, where the sun burns straight down onto it.

Then get home quickly. Put her straight into the cage and mist the walls of the cage with water so she can rehydrate right away. That is the first thing she needs after the trip, before anything else.

Getting her to lay

Butterflies are heliophilic. Sunlight is what drives them, and a female in a cage that never sees the sun will usually lay nothing at all. Getting the light right is most of this job.

Give the cage a few hours of direct sun a day, and no more. A window sill indoors is close to ideal, because the sun reaches the cage for part of the day and leaves it alone for the rest.

Just as important: shade part of the cage. She has to be able to get out of the sun, hide, and cool down. A cage standing in full sun with nowhere to retreat will kill her, and a dead female lays nothing.

Set up an airy mesh cage with the foodplant inside, cut and standing in that jar, and cover the floor with paper. Arrange the plant so it touches the sides of the cage. Females walk the walls of a cage, and a female walking the wall that meets the plant lays an egg on it. A plant standing on its own in the middle of the cage gets found far more slowly.

Cage size matters here, and bigger is not better. For smaller species the one I reach for is the 30 x 30 x 30 cm cage. In a cage that size the female runs into the sugar solution and into the foodplant almost immediately, which is exactly what you need her to do. Put a small butterfly in a large cage and she can spend days finding neither.

Bigger, stronger fliers do need the room. For something like a swallowtail (Papilio machaon), go up to the 40 x 40 x 60 cm size.

One trick from my own practice: put a meadow flower from the exact spot where you caught her into the cage alongside the foodplant. It costs nothing and it often tips a reluctant female into laying.

Then be patient. Most butterflies do not start laying until the second or third day in captivity. An empty cage on the first evening means nothing at all.

One useful exception: the browns do not need a foodplant to lay. They will start dropping eggs on the walls of the cage whether or not there is a plant in there.

Feeding her while she lays

A female may lay over several days, and a laying female has to be fed. This part is not optional.

Here is the setup I use, and it beats everything else I have tried:

• Dissolve ordinary white sugar in water, about one part sugar to nine parts water.
• Take the lid off a jam jar and put a piece of cotton wool in it.
• Pour the solution over the cotton.

She lands on the cotton rather than in the liquid, so she never gets stuck or gummed up, and she drinks through it comfortably. You do not need to show her where it is. Females find it in the cage on their own.

Two things to watch:

• Replace it every two or three days. After that it starts to ferment and go moldy.
• Top it up once a day. In the sun it evaporates fast. A splash is enough.

If she will not feed on her own, feed her by hand. It looks alarming the first time and it is simple:

1. Pick her up by the underside of her closed forewings while she is active.
2. Uncoil her proboscis gently with an entomology pin.
3. Touch the tip of it to a drop of the solution.
4. Repeat until she starts drinking by herself, then let her go.

Keep feeding her as long as she is laying well. When she slows down, take her back to where you caught her and release her. She can still lay there.

From eggs to caterpillars

Where the eggs ended up decides what you do with them.

Eggs laid on the foodplant stay on the foodplant. Leave them there and let them hatch where they are. Picking them off is the fastest way to ruin a clutch that was doing fine: handled eggs lose humidity and then simply never hatch.

The ones you move are the eggs laid somewhere else, on the cage walls or on the paper on the floor. Eggs on the paper travel with the paper, which is exactly why the paper is there. Where you really do have to lift an egg, use a damp brush and be gentle, and if several are clustered on one leaf, move the leaf instead of separating them.

Anything you have moved goes into a transparent container lined with absorbent paper, so you can check on it without opening everything up. Hold three conditions: enough humidity that the eggs do not dry out, enough ventilation that they do not go moldy, and no direct sunlight.

When the plant dries out under them

Cut stems standing in water eventually give up, and by then you may have newly hatched caterpillars all over them. Freshly hatched caterpillars are far too small and fragile to pick up.

Lay a fresh plant against the old one so the two touch, and let them walk across by themselves. They will find the new food on their own. Then take the spent plant out.

Once they are bigger you can handle them directly. Collect them carefully off the old plant, swap the plant for a fresh one, put them back in the cage, and they will climb back up onto it.

As they grow, sort them and move them into larger containers, and finally into a mesh cage. Feed fresh foodplant, and clean out droppings, old food, and excess moisture.

The daily routine, and the two ways people lose a brood

Clean the cage every day. Droppings and old food are how disease and parasites take hold.

While you clean, sort the caterpillars by size and keep the small ones away from their larger siblings. Small caterpillars kept among big ones can simply die.

Two habits that save specimens. Never pull a caterpillar off a dried-out plant; let it crawl across on its own, or move it along with the piece of plant it is sitting on. And never disturb one that is molting.

Then the two real killers:

Direct sun on a plastic or glass container. Even a short spell can cook an entire rearing. This is the fastest way to lose everything, and it happens to people who did everything else right. Airy mesh cages are fine in sun, as long as the heat does not wreck the foodplant.

Caterpillars reaching the water. Back to the cotton wool. It is the cheapest insurance in this whole guide.

Pupation and emergence

Most species go from caterpillar to adult in a few weeks, and this stage asks almost nothing of you. Keep humidity sensible, do not let anything dry out, and leave them alone.

There is one moment, though, where you have to stop handling them completely.

Once a caterpillar has hung itself up, leave it alone

When a caterpillar is ready to pupate it stops eating, wanders off the food, and settles on a stem or on the wall of the cage. There it spins a small pad of silk and hooks its rear end into it. In some families it also spins a fine silk girdle around its middle and sits upright in that sling; in others it just hangs head down.

That silk pad is the anchor for everything that follows. When the caterpillar sheds its skin for the last time, the tip of the pupa's abdomen carries a small hooked structure called the cremaster, and the cremaster locks into that pad of silk. It is what holds the pupa in place for the next weeks, and later it is what the pupa hangs from while the emerging butterfly pulls itself out and expands its wings.

So when you are changing the foodplant and you find a caterpillar that has stopped eating and attached itself, leave it exactly where it is. Do not pick it off with the others, do not move the stem it is sitting on, do not tidy around it. Break that attachment now and the pupa cannot form properly, and you lose the animal.

Then one morning the wings show through the pupal case, and a few hours later there is a butterfly drying its wings in your cage. That is the payoff, and it does not get old.

A brood started late in the season may overwinter as small caterpillars, but that is a choice rather than a rule. Kept warm indoors, many autumn broods run straight through to adults without any pause at all.

Letting them go

Take the adults back to the meadow the mother came from and release them there.

This is the part that makes the whole thing worth doing. You are returning far more butterflies than that brood would ever have produced in the wild, to the exact population they came from. No alien species, no foreign genetics, just more of what already lives there.

Doing it with children, and in the classroom

If you want one project that teaches more than a term of pictures in a book, this is it.

The whole cycle runs in weeks, not months, so children stay with it. There is something visibly different to look at every few days. It gives them a reason to learn a plant, to be careful with a living thing, and to keep a routine, because the cage genuinely does need cleaning every day.

It works as a school project and it works in kindergarten, with the caveats you would expect: an adult handles the net and the catching, the cage lives somewhere it will not be knocked over or cooked in a sunny window, and everybody washes their hands afterwards. The release at the end is the part the class remembers.

What you need

Not much, and most of it lasts for years.

• A butterfly net, ideally with a telescopic pole
• A portable field cage for carrying caught females home
• A breeding mesh cage for laying and rearing: 30 x 30 x 30 cm for smaller species, 40 x 40 x 60 cm for swallowtails and other large fliers, or a cylindrical cage if you want to stand a tall plant upright
• A mesh breeding bag for the smallest caterpillars, which slips straight over a branch or a jar of cut plants
• Soft tweezers for moving caterpillars without hurting them

Plus a jar, cotton wool, a small brush, and paper. That is the whole list.

FAQ

Do I need a garden or planted foodplants? No. Cut stems in a jar of water work for the entire rearing. Plug the jar neck with cotton wool so the caterpillars cannot reach the water.

Which species should a beginner start with? The commonest ones you can find locally. In Europe the clouded yellows, whites, marbled whites, walls, meadow browns and blues are all straightforward. In North America the local whites, sulphurs and satyrs are the same kind of easy. Leave rare species until later.

Can I start without catching a female at all? Yes, and it is the fastest way in. The nettle-feeding nymphalids, peacock, painted lady, red admiral, map butterfly and small tortoiseshell, lay in batches, so their caterpillars sit in big communal nests spun into the tips of nettle plants. One nest can hold fifty to a hundred caterpillars. Take a portion, put them on fresh nettle in a cage, and you are rearing the same afternoon.

What size cage do I need? For most smaller species, 30 x 30 x 30 cm. A small cage is an advantage at the laying stage, because the female finds the sugar solution and the foodplant right away. Step up to 40 x 40 x 60 cm for large, strong fliers such as swallowtails.

My female is in the cage but she is not laying. Is the light wrong? Very likely. Butterflies are heliophilic and a female that never gets direct sun usually will not lay. Give the cage a few hours of sun a day, and shade part of it so she can get out of the heat. Also give it time, most butterflies do not start until the second or third day.

What is a cremaster? It is the small hooked structure on the tip of a pupa's abdomen. Before pupating, the caterpillar spins a pad of silk and hooks itself into it; the cremaster then locks into that same pad and holds the pupa in place until the butterfly emerges. A caterpillar that has attached itself like this must not be moved.

Do I need a perfect specimen to breed from? No. For laying, condition is irrelevant. Save the perfect specimens for a collection.

How do I know if I caught a female? Check the abdomen first, it is noticeably larger and fuller. Then the outer margin of the forewing, usually more rounded. Where males have feathered antennae, feathered means male.

She will not lay anything. What am I doing wrong? Possibly nothing. Make sure the correct foodplant is in the cage, add a meadow flower from the site where you caught her, keep her fed, and give her time. Some females simply take a while.

What is the most common way to lose a whole brood? Direct sun on a plastic or glass container. It overheats in minutes. Second most common is caterpillars drowning in the water you are using to keep the foodplant fresh.

Is it safe to release the butterflies I reared? Yes, as long as you caught the female locally and release the adults at the same site. They are the same population and the same genetics, so there is no risk of introducing an alien species or a foreign genetic race. It is a straight benefit to the local population.

Is this suitable for children? Very. The cycle is short enough to hold their attention and there is something new to see every few days. An adult should handle catching, and the cage needs a spot where it will not be knocked over or left in the sun.