monarch butterfly life cycle

Monarch Butterfly Life Cycle

What came first, the butterfly or the egg?

Adult female monarch butterfly on butterfly bush

On a nice sunny afternoon I watched a monarch butterfly flitting from milkweed plant to milkweed plant. After a few minutes she went to a butterfly bush, had a sip from the flowers and went back to the job at hand. She was laying eggs.

I have 3 distinct milkweed patches and she visited all three.

Later, after she'd left, I went looking for the eggs hoping to gather some and raise them to adult safely in the house, then release the new butterflies.


Monarch butterfly egg

This butterfly stopped at about 20 leaves in a half hour then went away. Later I was able to find about 15 eggs (and a tiny just hatched caterpillar.)

Almost all the eggs were on the underside of the leaves. One was on the top and one was on a seedpod stem.

The eggs are quite tiny, less than 1 mm. They are a translucent pale yellowish colour and have a marked pattern on the end that can be seen with a loupe. The other end is stuck to the leaf.

According to Dr. Karen Oberhouser, an exceptional Monarch butterfly has been observed to lay over 200 eggs in one day. In average a female will lay about 700 eggs in her life but a number of over 1150 was observed. This varies on conditions. If too hot and dry or too cold, they will lay fewer eggs.

An adult monarch lives between 2 and 6 weeks and will lay during this whole period.

The Monarch egg hatches 3-4 days after being laid. If it's really cold they can stay in their egg for up to 8 days.

Newly hatched first instar larva

This newly hatched tiny larva or caterpillar, is not quite 2mm long. He is about to start varaciouly eating. This is pretty much all he will do (along with pooping) for the next 2 weeks. Caterpillar waste is called frass.

Monarch butterflies must have milkweed in order to complete their life cycle.

It has been found however that the 5 th instar, that is a caterpillar that has molted 4 times and who is within 4 days of pupating, will eat other foods including pumpkins and fresh cucumber. Here is an article about monarch larva eating pumpkin and having orange frass.

There are many varieties of milkweeds. All seem to be acceptable food which allow the monarch butterflies to complete their life cycle. I just chose a variety that grew around my area and this is working well.

The milkweed flowers feed many different kinds of insects including honey bees, many varieties of butterflies and countless little flies.

Monarch feeding on goldenrodMonarch adult feeding on Liatris

Although the larvae must have milkweed, the adult monarch will eat from a large number of flowers.

In my garden the Liatris and butterfly bush are well loved. Later the goldenrods are much prized as is the blue clover. In between many of the the wild flowers seem to attract butterflies and bees.

The larva will eat, poop and molt 4 times.

When he first emerges from his egg until he molts for the first time, he is a first instar. After his first molt he becomes a second stage instar, and so on.

When he molts he goes sort of quiet, his legs seem to go limp and he wiggles out of his old skin head first having made a new larger skin. He will then probably eat his old skin.

The words Larva is a general term that refers to all insects that goes through the egg-larva-pupa-adult type of life cycle. Caterpillar is used for moths and butterfiles. Scientists tend to say larva rather than caterpillar.

The newly hatched larva will start by eating the fuzzy hair on the bottom of the leaf then will go on to the leaf itself. It makes an arc-shaped hole in the milkweed leaf. One way of finding small 1st instar larva is by looking for these holes.

Life cycle of monarch butterfly

The larva will molt in 1 to 3 days, the timing depends on the temperature.

The second instar larva continues to eat voraciously and molts in 1-3 days depending on termperature.

Same goes for the third and fourth stages.

The 5th instar larva are the largest and fastest of the stages of the monarch. At the end of his cycle he will often get off the milkweed and go several meters away looking for a place to pupate. This larval stage varies between 3 to 5 days.

The newly hatched monarch caterpillar is very small and translucent. He is not heavily coloured and the bands are barely visible. As he goes through each molt, the larva gets better defined colour bands and grows quickly.

Monarch Butterfly Pupates

monarch caterpillar is attached

After finding a suitable spot the larva attaches itself and takes on a sort of bent j-like position. The Monarch Caterpillar spins a silk pad and attaches it to the support and dangles up side down. He has a sort of handle at the rear end called a cremaster.

In this case the larva is attaching itself to the frame of the enclosure he has been living in. There are many predators in my yard and I protected him from wasps and other parasites and from whatever might like to taste him

Monarch caterpillars are poisonous to most birds and taste bad but to learn that the birds have to taste at least one.


monarch crysalid

Gorgeous jewel-like crysalis (or crysalid) of pupating monarch butterfly.

And now we wait...

The pupa or crysalis stage lasts about 10 days. Towards the end the wing patterns start showing through the casing until the colours are fully visible.

Many moths and butterflies spin a silk cocoon to pupate in but this is not the case for monarchs. This is a skin enclosure, it was quite soft but hardened as it became exposed to air. The corect term is crysalis or crysalid.

Although it looks like nothing is happening, there is frantic activity inside the crysalid. The caterpillar parts that are not required anymore are being re absorbed and new organs are being made. The caterpillar had very basic organs or rather not much more than cells waiting to develop into caterpillar parts. In the crysalids these are stimulated and grown or modified into a butterfly.


freshly emerged monarch butterfly

When ready, the pupa splits the crysalid and a wrinkled up adult gradually emerges.

Gradually the wings unfold. An alarminly blue fluid is pumped through the wings to stiffen them. They gradually stiffen and harden into shape. The first time I saw this happen I though something bad had happened as a drop of sticky blue fluid dripped from the butterfly. This is normal I think.

As this happens the butterfly slowly beats his wings. It takes a couple of hours before the wings are ready to be used.

Eventually the freshly minted fully adult butterfly flies off to find a mate and start the life cycle over.


Wait! In the fall something different happens

In the fall when days are getting shorter, newly emerged butterflies are not fully mature and are not capable of breeding. Instead of finding a mate and laying eggs, they fly around eating greedily and fattening up making reserves for their yearly migrations.

Their life cycle changes. During the summer, when the days were long and food was abundant the normal life cycle happened but in the fall a delay mechanism kicks in to stop the pupa from maturing fully. The trigger is not fully known. It's possibly a combination of factors, food composition, daylight length, temperature?

The summer breeding butterflies life 2 to 8 weeks while the fall-winter butterflies can live up to 9 months.

The Big Migration

Monarch cannot survive the winter so they migrate. The take a winter holiday in Michoacan, Mexico, and in California. It's not much of a holiday when you have to fly a couple of thousand miles though. One particularly athletic butterfly was clocked at 265 miles in one day, most average between 50 and 100 miles though. Depending where they start from monarch butterfly can take 2 months to get south.

They have a built in instinctual GPS using a combination of clues such as sun/moon and magnetic field of the earth to navigate. They are not remembering because the migrating butterflies have never done this before.

In the spring when the days are longer the monarch butterflies start their journey home. They complete their life cycle and mature. They breed and lay eggs.

Even though the butterflies that migrated south for the winter did the trip in one go, the returning butterflies will not do the whole trip. Instead they will lay eggs along the way and their children will continue the northern migration. It only takes 4-5 weeks for a full monarch life cycle to complete so fresh energetic butterflies are ready every month after the start of the migration. Although the fall butterflies lived up to 9 months, these new breeding spring butterflies only live 2-6 weeks.

This need to stop and breed and raise a new generation of butterflies means that there has to be a steady supply of milkweed all the way up. The adults also have to feed and need flowers to nectar on. This has been a problem because of drought, spraying of weeds and development.

The wave of advancing butterflies is monitored and you can see the progress of the monarch butterflies as they come north. Learner.org has a map Journey North

Is it a boy or a girl?

Male monarchFemale monarch

It's very simple to figure out if a monarch butterfly is a male or a female. Look at the wings. The males have a dark spot at the lower end of their wings on one of the veins near the body. The female does not have these spots. There are also small variations on the end of the thorax and the female has somewhat thicker veins.


Raising monarch butterflies from eggs

They are easy to raise if you are careful. Read my page on raising monarch butterflies from eggs.

It's a great summer project to do with kids too.


I try to be accurate and check my information, but mistakes happen.

email me if you find mistakes, I'll fix them and we'll all benefit: Christine