Monarch Butterflies on Our Swan Plant (Milkweed)

Monarch Butterfly Female

Female Monarch Butterfly, freshly hatched

This year, our swan plants have grown, and they were very attractive to the monarch butterflies which pass through our yard, so much so that the monarch larvae (caterpillars) devastated our two swan plants. It was fascinating watching their life cycle.

Swan plants are a type of milkweed, and milkweed is the favourite (some say, only) food source for the monarch butterfly caterpillars. There are very few other plants that can sustain the caterpillars, especially pumpkins, but milkweed has a special chemical that the monarch needs to metamorphose from caterpillar into a butterfly.

Monarch Butterfly Egg

Freshly laid egg of a monarch butterfly

When the monarch butterfly lays its egg, it is opaque and creamy yellow.  (I watched the mother monarch lay this egg and then immediately photographed the egg.  I didn’t want to get too close to the mother for fear she would depart, so I didn’t photograph her.)

Monarch Butterfly egg about to hatch

Minutes from hatching

After three or four days, when the monarch butterfly egg is ready to hatch, it turns more transparent, and you can then see the larva (caterpillar) inside.

freshly hatched monarch butterfly larva (caterpillar)

Monarch Butterfly freshly hatched, eating its eggshell

When the monarch butterfly caterpillar/larva first hatches, it is opaque-white with a large black head.  Its first meal is its own eggshell.  Shortly, however, it gains a bit more colour, though not much during its first instar (caterpillar stage).

monarch-butterfly-eaten swan plant

Leaf after baby monarch caterpillar has been eating (notice at right the whitish remnants of the eggshell)

baby monarch butterfly caterpillar (larva)

baby monarch caterpillar

All the monarch larvae (caterpillars) do during their two to four week life is eat and grow, eat and grow, eat and grow.  The entire life of a caterpillar is two to four weeks, depending on the temperature.  During colder weather, they grow more slowly.

2nd or 3rd instar of monarch butterfly larva

Third instar ( I think)

During the second and third instars, the monarch caterpillar has its famous black, white, and yellow stripes.

4th instar of monarch butterfly caterpillar

Fourth instar

During the fourth and fifth instars, the caterpillar has longer antennae.

5th instar of monarch butteryfly larva

Fifth instar

The fifth instar will attach its legs to a stem or leaf and weave a cocoon around itself.

chrysalis (cocoon) of monarch butterfly

Monarch Butterfly Chysalis

Monarch Butterfly Cocoon (Chrysalis)

Chrysalis (Cocoon)

The monarch will then remain in the cocoon (chrysalis) for approximately ten days before emerging as a full-grown monarch butterfly.



Female Monarch Butterfly

Female Monarch Butterfly (a few minutes after exiting chrysalis)

This is a female, since she has the thicker black lines in her wings and does not have the two black dots on her hind wing that the males have.

Closeup of Monarch Butterfly legs

Notice her legs, which are used to find nectar as well as hanging on to plants

After the leaves grew back on our swan plants, I am sure she laid some of her 300 to 400 eggs on our plants, though the next generation didn’t have as many caterpillars and so didn’t devastate our swan plants like the first generation did.


chrysalis (cocoon) of monarch butterfly after releasing butterfly

Emptied Monarch Butterfly Cocoon

leafless swan plant after being eaten by monarch butterly larvae

One of Our Leafless Swan Plants

We had so many monarch butterfly caterpillars on our two swan plants that they literally devastated our plants, removing all the leaves and eating many stems and seedpods.  Unfortunately, since I didn’t realise how much each caterpillar will eat, I simply watched in awe of the growing caterpillars.

swan plant with monarch butterfly larvae

How many caterpillars can you find? (Click to Enlarge -- Answer at bottom of post)

It wasn’t until it was too late that I realised that they were going to run out of food before they all grew large enough to metamorphise into butterflies.  We ended up having only two cocoons on one of our swan plants, and none on the other.  All the rest of the caterpillars died of starvation.

Here in New Zealand, there are four generations of monarch butterfly each summer.  The monarch butterflies will live two to six weeks during the summer, but then the fourth generation will live the entire winter until the next spring, at which time they will lays eggs and begin the cycle all over again.

We harvested some of the seeds from our swan plants this year and are beginning to grow seedlings that we can then plant around our place.  I’m also going to try to grow swan plants from cuttings that I will take from our two original plants.  The monarch butterflies are a beautiful sight, especially when there are several of them flapping around our yard.

When I first saw the monarch butterfly larvae growing on our swan plants, I wondered how far they would migrate for the winter.  It turns out that New Zealand monarch butterflies don’t migrate at all.  They spend their entire lives here.


swan plant with ten monarch butterflies

I found 10. I also highlighted a chrysalis. (Click to enlarge)


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4 Responses to Monarch Butterflies on Our Swan Plant (Milkweed)

  1. Pat Dygula says:

    Just a note to say I see you are posting again after such a long time. I was wondering if everything was OK.
    Windows installer doesn’t work on my Win7, so tomorrow I plan to reformat and reinstall. Wish me luck. I hope I don’t lose any information.
    I don’t know if you keep in touch with Vicki but she decided to leave Guadalajara and move back to Canada near her daughter.
    Best wishes,

  2. Colin says:

    Hi Dave
    It was great to read your excerpt on the monarch butterfly – I learnt a great deal and I thought your up-close photography was fantastic. I’ve seen monarchs fluttering about in winter time and never realised they were ‘wintering over’. How sad that so few of your caterpillar population made it to butterfly status. Sounds like you will be providing a lot more fodder next year though how you will prevent yourselves from hosting millions of lavae, I’m not sure. Will you bring out new plants in succession through the session like different courses in a meal?
    Great to hear that your spring is lasting as you have lot of plants and trees to maintain.
    Blessings to you both.

  3. RoNZ says:

    Have three swan plants that would normally be eaten by Monarch caterpillars… this year only two caterpillars have survived… the rest harvested by wasps before getting much bigger than 5-10mm. Have noticed 3-4 species of wasp; mostly what look like paper wasps.

    Is this a common occurrence?

    • Dave Clingman says:

      Hi RoNZ. Yes, unfortunately, wasps consume massive amounts of eggs and caterpillars. I’ve lost hundreds to them this year. They seem especially bad this year. Some things you can try are:

      1. Create a wasp trap (soda bottle top 1/3 cut off, reversed and inserted and stapled to the bottom 2/3, and then sugar water inside — but will this also attract bees?)

      2. Grab the eggs or caterpillars when you find them and bring them inside or somewhere safe to let them hatch and grow. Perhaps a potted swan plant you’ve got growing inside the house or greenhouse?

      3. Cover the swan plant that has one or more eggs or caterpillars, so that wasps cannot get to them. I use shade cloth, but a thin, light cloth that lets in light and air would work.

      4. If you can find a wasp nest, destroy it at night when all the wasps are there. I usually use a regular fly spray but I have also simply crushed them while wearing thick gloves.

      Check out the Monarch Butterfly New Zealand Trust forums for more ideas, or ask questions there. Lots of people there to help.

      Anyone else have any ideas?