How to Grow Monarch Caterpillars from Eggs to Butterflies Indoors
It is truly amazing what kinds of experiences you can bring inside that would normally take place outside. Growing monarch caterpillars indoors is one of those super cool experiences! If I’m being totally honest, it’s pretty easy to do too, and will give you more confidence in rearing other insects, like honeybees, if that is something you’re into. Check out my step by step tutorial on raising monarch butterflies from eggs.
Monarch butterflies have a life cycle that is pretty similar to other insects. There are several hatchings of monarch butterflies throughout the summer (usually four or five successions). The one coming up is the fall, and fifth/final hatch, which in my opinion is the coolest and most important succession. The butterflies that are hatched between August/September are the ones that fly from the Midwest to Mexico where they overwinter. This generation of butterflies lives so much longer than the other generations of butterflies, and the reason this is, is not well known in science. In order to get the monarch butterflies that fly to Mexico you need the ones flying around now (July) to lay eggs.
What came first, the butterfly or the eggs. We may never know, but for this post, let’s start at the egg stage. Eggs are laid *usually* on the underside of a milkweed leaf or on the stem by a female monarch butterfly. It all depends on how windy it is that day! I had the opportunity to learn how to rear monarch caterpillars, and create the ideal conditions to “force” monarch butterflies to mate. (That can be a different post for another day). Did you know that you can visually see the difference between male and female monarch butterflies? Remember: boys have dots, girls do NOT. You can see the dots when the wings are open, however, you are more likely to see a monarch with it’s wings closed. So, being able to tell from the backs of their wings is important.
Check out this video to see what a monarch butterfly’s egg looks like before it’s ready to hatch!
Now, I probably did a little oopsie in this video-live and learn. I picked the milkweed leaf and put it on a petri plate with agar, and it still almost dried out!! Agar is a semi-solid liquid, almost similar to gelatin. I would recommend trying to catch monarch caterpillars (“cats” for short) right after they hatch to start raising them indoors.
After that you can move a caterpillar into its own petri plate/cage. BUT please note, monarch caterpillars are cannibalistic. They WILL try to eat each other, and they get pretty territorial about their space. So, to get the best quality caterpillar and ultimately butterfly, you will want to separate them! I once put a bunch of caterpillars in a cup together as I was picking them off of milkweed plants, and that was a HUGE mistake. They ended up forming bruises on their bodies, which looked like little black dots, then died as a caterpillar, or if they formed as a butterfly, many turned up deformed, and couldn’t fly! You don’t know what you don’t know.
You can tell a monarch caterpillar apart from a black swallowtail butterfly by their markings. Swallowtail butterflies have black, yellow and white patterns, but have dots. Monarch caterpillars have solid black, yellow and white stripes ONLY. Also, swallowtail butterflies have different host plants. A host plant is the plant that the butterfly will lay eggs on that the caterpillar will hatch and feed on. Swallowtail butterflies use a wider variety of plants as host plants, such as: dill, Golden Alexander, fennel, parsley, Queen Anne’s Lace, celery, carrots and more. However, the monarch caterpillar’s only host plant is milkweed. The eggs might be laid on other plants, but then they would have to travel to find milkweed, as that is their ONLY food source. (Picky little things!) More often than not, monarch butterflies lay their eggs on milkweed plants.
As monarch caterpillars feed on milkweed, they go through five caterpillar stages, called instars. With each instar the caterpillars shed their skin and get bigger. This happens very quickly, and you’d be surprised how much they can eat! If you want to grow monarch caterpillars indoors you must have a clean source of milkweed. Any type of milkweed will do, but it MUST be milkweed for monarch caterpillars. They will not eat grass, or carrot tops, or leaves…ONLY milkweed. The most commonly found milkweed in the midwest is Common Milkweed (shocker, right?!). This type of milkweed has large oval-shaped leaves that produce a purple umbel of flowers that is sweet smelling. Other types of milkweed that you might find, and/or that you could plant in Iowa, include: Swamp Milkweed, Showy Milkweed, Whorled Milkweed, and Butterflyweed (sometimes called orange milkweed).
I also mentioned that your milkweed must be clean. What I mean is that you need to find some that hasn’t been sprayed in the road ditch accidentally or intentionally by farmers or county workers. I do NOT recommend getting milkweed from a place that could have had drift from a nearby crop field either from spraying on the ground or by aerial spray. Now, when we grew monarch caterpillars through research protocols, we also washed our milkweed in a 1:100 part bleach to water solution. That is 1 Tbsp bleach to 1 gallon of water. However, there were plenty of times that we didn’t take the time to use bleach, but just put them in a bucket of clean water, swished them around and shook them to dry. We were a little extra, and had a separate, specified milkweed salad spinner to use to get these leaves as dry as possible.
When picking milkweed you will want the most tender, youngest leaves, because that’s what the caterpillars like the best. Anything that has a blemish on it, leave it in the field. We would often avoid the top cluster of leaves, then pick the next four to six leaves depending on how big the leaves were. You can also pick several leaves, wash them, and wrap them in damp paper towels and put them in a zip lock bag for three to four days, AND put them in the fridge to avoid having to pick and wash every day. That worked well for us!
After getting the milkweed from your trusted source, washing it, and drying it, you’re ready to put the caterpillar on your milkweed. Depending on the size of the caterpillar you’ve found you’ll want to either grow it in a petri plate, WITH a lid, or a combination of a petri plate and a clear drink tumbler! These caterpillars will NOT stay confined in the space you want and will crawl everywhere. So, put the top ON!
If the caterpillar is small, smaller than the diameter of a computer cord, you’ll want to put it in a small petri plate, with a lid. Then using any old regular scissors, cut sections of the milkweed leaf to fit in the petri plate. Make sure the leaf fits well within the boundary of the petri plate. If there is a gap in the lid, the caterpillar will disappear. Often times we cut on either side of the main stem of the milkweed leaf, toss the stem, then cut three or four sections out of the leaf.
Once the monarch caterpillar gets to be about the diameter of a computer cord, and eating more than one section of leaf a day we moved them into clear tumbler-style drinking cups, fitted with a piece of filter paper and a petri plate. Don’t worry, a coffee filter cut to fit the petri plate works too. You just need something between the cup and the petri plate, otherwise your caterpillar will suffocate. If raising a lot of caterpillars at one time, I would recommend getting plastic food service trays to put the petri plates and cups on. I’ll put links to all the materials I used to grow monarch caterpillars indoors at the bottom.
When the caterpillar moves into the cup you can also start giving them a whole leaf wrapped around the perimeter of the cup. Phew, this will give you a break in feeding! Something that you will notice is that caterpillars poop a lot!!! That poop is called frass, and as far as I know, it isn’t good for anything, so dump that out into your garbage daily. If you don’t it could mold. Insects and mold don’t go well together. I suppose you could dump it on your garden, though I’m not sure it provides any benefit, but it couldn’t hurt, right?!
The next step in growing monarch caterpillars indoors is to wait for it to start to make its “J.” The caterpillar will move to the top of the cup and start spinning a web-like material across the top to be able to hold the chrysalis. Once it makes its “J” leave. it. alone. This will help it form properly into the chrysalis. The chrysalis is the green “shell” looking thing that forms in which the caterpillar hides in for 12 days before turning into a butterfly.
Once it’s fully into the chrysalis you should remove the milkweed leaf and throw it away. Sometimes the caterpillar will make the chrysalis on a milkweed leaf. While this is not ideal, you can fix it! Gently peel the chrysalis and the web-like material off of the leaf and use scotch tape/clear tape to tape it to the top of the cup. There have been a couple of times the chrysalis has fallen and doesn’t have any webbing left. You can use some hot glue, just on the black portion of the chrysalis, and attach a piece of yarn or string, and then hang from the top of the cup. Having the chrysalis hang is really important to proper wing development as well. Do not leave it on the ground, it usually doesn’t turn out well for the butterfly.
The chrysalis will sit there for about 12-15 days until it will turn black, then translucent, and you’ll start to see bits of orange in the chrysalis. Surprisingly this is GOOD! Pretty soon the monarch caterpillar will emerge from the chrysalis! Check out this video for a time lapse of this happening!
After the butterfly comes out of the chrysalis you will notice that it will have a large, swollen abdomen, which is normal!! Check out a video here-this chrysalis fell, so we reattached it with some hot glue and dental floss. The abdomen is filled with fluid that will pump into its wings, and the extra that isn’t needed for the wings to develop will drip out of the monarch butterfly. Leave it to dry in the cup, undisturbed for at least 12 hours, if not 24 hours.
Then when releasing the monarch you can find a nectar filled flower to set it on, and yes, you can touch a butterfly. We have tagged hundreds of monarch butterflies. All of them have to be touched in order to place the tag. The tag is a sticker with a series of letters and numbers on them. In order to properly hold a monarch butterfly make sure its wings are together. Did you know they actually have four sections of wings?! So, just make sure they’re all together. It’s great if you can place the wings at a diagonal between your pointer finger and middle finger on the sides of your fingers.
If it is the spring, and you are keeping the butterflies in a monarch cage for the summer with milkweed and other nectar plants, you will likely need to feed them. You can feed them full force white Gatorade. By full force, I mean, it needs to have the sugar in it. It cannot be G2 or something with lesser sugar. ALL of the SUGAR! Get a shallow dish, like an indoor pot saucer, and put a pot/pan scouring pad on it and put about a half of an inch of gatorade in the bottom. They will use their proboscis (tongue) to suck it up, which is pretty cool to watch!
Before releasing the monarch butterfly that you grew indoors from a caterpillar you should, if at all possible, check to see if it has a parasite that is detrimental to the monarch butterfly. This parasite is called OE for short. OE stands for Ophryocystis elektroscirrha. The only downfall is that you have to have a microscope to be able to do this. You need transparent scotch tape (not the regular, cheap kind of scotch tape, the expensive see through, vanishing tape) in order to take a sample from the monarch butterfly’s abdomen, apply it to a microscope slide and look for the football shaped spores.
After the monarch butterfly has dried for 12-24 hours hold the wings together and then touch the tape to the abdomen of the monarch and place it on a microscope slide. Looking through the microscope you will see large oblong shaped scales, which is normal. What is NOT normal is seeing little football shaped dots within the scales, that is the parasite! If you find that your butterfly has the OE parasite, it is important to ethically put down this monarch by placing it back in the cup and then placing it in the freezer. This kills the insect, and therefore, stops the spread of this parasite. This is just as important as making sure a cow that is going to the locker is able to walk through the gate before being killed for slaughter. You don’t want to pass a disease from one animal to several others, and the same goes for the monarch butterfly. You can learn more about the OE parasite here from the University of Georgia.
When you have determined that your monarch butterfly is healthy, dried, and ready to be released into the wild it’s best to wait for a day when there isn’t rain. You can take it to a nectar plant (anything that has a fresh bloom) and set it on it. It should want to take a drink a bit before it flies off. Remember though, butterflies fly up, so don’t stand directly over where you release the butterfly (just so you don’t take it to the face). Then it will be up to the monarch butterfly to trust its instincts to find habitat, lay eggs, mate, or fly to Mexico. If you’re interested in tagging butterflies, reporting tags, viewing recoveries, and more feel free to check out info at monarchwatch.org
Here is a list of materials that may help you with growing monarch caterpillars indoors. These items are not necessary, but do remember to keep caterpillars separated, or give them enough space and resources so they don’t have to fight and damage each other.
List of materials needed to grow monarch caterpillars indoors:
- Small petri plates
- Large petri plates
- Filter paper
- Optional, but nice to have things if you want to do this more than once:
I hope you enjoyed learning about bringing monarch caterpillars indoors to take care of and watch this truly amazing life cycle.
Until then, please join the “Dirty Fingernail Club.” If you’re in Iowa or nearby states, be on the lookout for other in-person homesteading classes. This is just the start of growing something good!