Raising Monarchs: Collecting & Protecting Caterpillars

As I mentioned in my last post, I’m writing up a few very basic tutorials to help those who wish to attract, raise and release monarch butterflies. The monarch numbers have declined by nearly 90% in the past few decades! Loss of habitat is a major factor as the milkweed that feed their larvae (caterpillars sounds so much cuter) has been nearly wiped out by widespread herbicide use (RoundUp) in farms, highways and meadows along their migration route. So in my last post I talked about buying, growing and planting pesticide-free milkweed, which gives monarchs a place to lay their eggs.


So now you’ve got your milkweed planted or in pots around the garden and they are filling up with caterpillars. At this point you can just let them do their thing and approximately 10-20% will reach adulthood. Pretty dismal numbers, right? Sadly, caterpillars have a very high mortality rate.

Once they reach adulthood, monarch butterflies are protected by the toxic milkweed they eat as caterpillars. Strangely enough though, the caterpillars themselves are a delicacy for lizards, spiders and birds. Last summer I actually rescued a big fat caterpillar from a spider’s den. I swear I turned my back for a minute and next thing you know the cat is being dragged into a hole in the ground! I grabbed the little guy and pulled him out and an angry spider came racing out after him! It was terrifying.

lots of monarch cats

There are more insidious threats too, including a parasitic protozoan called oe, tachinid flies that lay eggs inside the cat, and wasps that lay eggs inside chrysalides as they are forming. All these reasons are why some of us have taken on the task of collecting “cats” and raising them in captivity. They are also ridiculously entertaining, so much better than TV! I have spent many a contented hour watching these little goofballs do their thing.

Tiny Baby Monarch Cataerpillar (1st Instar)
Tiny Baby Monarch Cataerpillar (1st Instar)

Raising these cats is fairly simple as long as you are willing to clean their enclosures and provide fresh food daily. If you meet those stringent requirements, it’s as easy as locating a caterpillar and moving him into a clean container. I like to let the cats hatch on the plants outdoors and wait until they grow a bit before collecting them. Many people simply remove the leaf with the egg on it and place it in the enclosure, it’s up to you.

Enclosures vary widly. I’ve used all types of things, from Mason jars to plastic containers from the grocery store to small “critter keeper” or reptile cages. As you can see below, a clear baked goods container (not that we ever have those on hand!) is perfect for smaller cats. I lay a piece of paper towel on the bottom and keep milkweed leaves fresh with a plastic container filled with water. Those little end plug thingies florists use are perfect but also a small to-go container with a hole in the top is fine.

Raising caterpillars in a plastic container
Raising caterpillars in a plastic container

When using a glass container it’s helpful to place a piece of paper towel down the inside for the cat to climb. In case the butterfly falls after emerging from its chrysalis it can also use the towel to climb back up.

Paper Towel down the side of a glass jar gives the caterpillar and butterfly an easy surface to climb
Paper Towel down the side of a glass jar gives the caterpillar and butterfly an easy surface to climb

Each day I set the cats aside, shake the poop out of the container and change out the paper towel. Be careful never to leave standing water or even a jar of water without plugging up the neck with towel or plastic wrap. Small cats will crawl down the stem and drown. IF you ever do discover a drowned caterpillar, here is a super secret tip: lay it on a towel and cover it completely with salt. Crazy, right? Caterpillars are capable of living for long periods without breathing. The salt will draw the moisture out of their bodies and more often than not they will be revived within minutes! It’s astounding, but I can unfortunately say from experience that it works.

Fancy enclosure
Fancy enclosure

If you want get crazy you can build a nice big enclosure for your caterpillars.We just built this new enclosure from old pallet wood, found doors and shade cloth. It’s big enough that I can keep the milkweed plants in pots, which makes cleaning poop much easier as it just falls in the dirt. It should have screen, wood, cardboard or something else on the sides and top for the cats to climb as they will look for a place to pupate that will allow their wings to stretch and dry after hatching. They will usually stay on or near the plant until they’ve eaten their fill then wander to the top of the enclosure to pupate.

Fancy does not equal secure - these guys are very sneaky!
Fancy does not equal secure – these guys are very sneaky!

Be careful though, these cats are super sneaky and will squeeze out any small opening they can find! Twice in one day I found this escapee outside of the enclosure. Naughty little monkey. Luckily they’re not that hard to catch.

Assuming your cats stay in their enclosure they will go through five stages known as instars. Each time they will shed their skin and come out looking a bit different. This can be a little freaky because they wander off then just stop moving for a long period, sometimes a whole day they will just sit there looking dead. Then suddenly they walk out of their skin and their face falls off! Seriously, it’s weird but again pretty cool. It’s important not to interfere with this process so try to resist poking them to see if they’re okay.

This guy's face is literally falling off!
This guy’s face is literally falling off!

If you have impeccable timing you may get to witness a cat eating its shed skin before returning to the milkweed. Apparently it’s a good source of vitamins and minerals. In the final stage, or 5th instar, monarch cats are 1-2″ long and about as thick as a pencil. They eat an absolute ton. If you, like me, are always low on milkweed you will start begging your biggies to pupate and leave some milkweed for the younger cats. In milkweed emergencies, 5th instar cats have been known to eat fresh butternut squash and cucumber or canned pumpkin.

Eventually the biggies will climb all over the place looking for a spot to pupate. I call this “going on walkabout.” The ideal spot will be an area where they are protected so they can hang securely for a couple of weeks until it’s time to eclose from their chrysalis. They also will need space around them so they can eclose properly and allow their wings to expand and dry.

This one is testing the space for pupation potential
This one is testing the space for pupation potential

When it settles into a spot it will attach itself with a silk “button” and hang in a J.


Over the next 24 hours or so an amazing transformation will occur. The cat will shed its skin and its insides will morph into a lovely, bright green chrysalis decorated with little gold dots. I just learned that the dots, which really look like gold leaf, are the channels that deliver oxygen to the caterpillar as it’s pupating!


Eventually the chrysalis will turn dark and in the hours before hatching you will be able to see the monarch’s orange and black markings through the clear outer shell of the chrysalis. If you watch closely you’ll be able to see it pressing from the inside and separating itself from the outer shell.

Just before
Just before “hatching” you will be able to see the monarch in full color

Eventually it will split the shell and out pops a butterfly! Some pop out fast, some slow. Some come out almost fully formed but others will eclose with tiny little wings and a big, fat abdomen. Don’t freak out, it’s totally normal. The monarch abdomen has fluids stored inside and you can actually watch as the monarch pumps fluid up from the abdomen and into its wings. You’ll even notice droplets of rust-colored liquid underneath where the fluid has dripped from the wing during the drying process. It’s freaking astounding.

monarch butterfly abdomen eclose
This guy came out with a fat abdomen and tiny wings which eventually stretched and dried

Sometimes the process isn’t quite so smooth. Any difficulty can be a sign of sickness and the butterfly should be monitored. If it can’t get out of the shell or can’t hold onto it once it’s out it is likely too weak to survive in the wild. Occasionally a healthy monarch will fall during eclosure. If it has something to crawl up, like a stick, a healthy monarch will manage on its own. On the other hand, a sick monarch may fall because it is too weak to support its own weight and even with help it will struggle through the process.

A monarch that emerges deformed or unable to support itself it may have oe, in which case it should be euthanized. That’s a really hard decision to make and I reserve it only for those that are in extreme situations. I think freezing is the best choice when that is necessary. It’s really painful for me but painless for the cold-blooded butterfly

This guy took his time
This guy took his time but ended up okay

This beauty popped out looking ready to fly! They’re my favorites.

This guy emerged fully formed
This guy emerged fully formed

Last week I had a wonderfully coordinated set of monarchs in different stages. They did me the favor of lining themselves up for a photo op. This gives you a good idea of what to expect through the process, from hanging J to chrysalis to eclosure.

monarch_pupation_trioI hope this has been helpful! There is a lot of great information online if you need more detail or just want to know more about this miraculous creature. I had planned to include a bunch of links but honestly it’s easier if you just type your question into a search engine and read whatever pops up. Feel free to leave questions, comments, insults or whatever below – I will gladly answer as best I can!

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6 Comments Add yours

  1. Pat Sherwood says:

    Extremely interesting. Thank you.


    1. Sheri Fox says:

      Thanks Pat 🙂


  2. Kathy Sturr says:

    Amazing! I loved reading this. As much as I would love to raise Monarchs I know I would be lacking on time and therefore, would be a bad mommy. Not that you haven’t given wonderful instructions and how to. I will rely on the Milkweeds in my garden and hope for 20%! As I was reading this I thought how terribly sad if we were to lose this amazing creature from the earth. I never knew the gold dots were oxygenators. I have so much respect and admiration for you!


    1. Sheri Fox says:

      I think with all the awareness out there the monarchs will survive! It’s very hard to imagine them disappearing. And I like to think 20% is low for survival. In a healthy organic garden with plenty of food I bet it’s much higher. Really cool about those gold dots isn’t it? I couldn’t believe it!

      Liked by 1 person

  3. jon@scraphound.net says:

    Awesome post, honey!     http://www.ScrapHoundStudio.com


    1. Sheri Fox says:

      Thx sweetie-pie 🙂


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