How to Raise Healthy, “Street-Smart” Monarch Butterflies

BACKGROUND

Like honey bees, bumble bees, and many other important insects, the number of monarch butterflies has been on a downward trend over the last several years. There are many reasons for the monarch's troubles, including loss of habitat, natural predation and disease, and even winter storms in Mexico where they annually congregate.

So, to try to give the monarch a leg up—well, actually, six legs up!—plenty of well-meaning people rear monarchs indoors and then release them into the wild. On its surface, this seems like a good idea. (Spoiler: it's not!) Left on their own in nature, only about seven to 10% of monarchs make it all the way from tiny egg to glorious adult. But in captivity? As long as you keep their environment clean and provide them with everything they need to thrive, as many as 90% or more can survive.

Sounds good, right? I thought so. I used to love to find monarch eggs, bring them indoors, nurture them to adulthood, and then release them into the wild. In my first year, I released 42 butterflies and thought I was pretty hot stuff as a result.

But here's the thing. While I'm neither a biologist nor a professional lepidopterist, I do occasionally get to pick their brains, and, while writing an article for Discover Magazine online, I learned that I was probably doing the monarch more harm than good. I was bummed.

Rather than stop raising monarchs altogether, I've modified my approach, based on what I've read and learned from the folks who work with these amazing creatures full-time. I'm sharing my methods here for teachers, scout troops, or anyone out there who would still like to raise a small number of monarch butterflies in a way that is less likely to add to the monarch's troubles in the process.

Step 1: Commit to Making Your Monarch Butterflies "Street-Smart" and Checking Their Health

One of the magical things about monarch butterflies is that in late summer/early fall they start their trip from Canada and the U.S. and head south to overwinter in Mexico. (The flight is about 2,000 miles in all!) But, in order for butterflies produced this time of year to know what they're supposed to do, they need to be exposed to certain environmental cues—environmental cues that they aren't likely to get from the great indoors.

ENVIRONMENTAL CUES NEEDED FOR "STREET-SMARTS"

decreasing day length
decreasing temperatures overall
more extreme day-night temperatures
deteriorating milkweed quality

I call butterflies that have been exposed to these environmental cues "street-smart," because they're ready to travel and are well-equipped to make the trip. Such cues are thought to flip certain switches on or off in monarchs. Instead of having fully developed reproductive organs and the urge to breed, they have the good sense to tank up on nectar and put on fat for their long journey.

By contrast, those butterflies I raised indoors—particularly towards the end of the season—probably emerged with breeding on their minds. They may never have even thought to fly to Mexico, because I made sure they had only the choicest milkweed and they were raised in an artificially lit, air-conditioned environment. (Oops.)

BUTTERFLY HEALTH

In addition to having street-smarts, you're going to want to make sure the butterflies you raise are healthy. There is a particularly nasty parasite called Ophryocystis elektroscirrha (OE for short) that wreaks havoc on monarchs. So, the last thing you want to do is raise a monarch that's ready to head to Mexico—only to infect the thousands of other butterflies it comes into contact with along the way.

Step 1 is simply being willing to commit to the extra work required to raise your monarchs outdoors and being willing not only to test for OE but to destroy rather than release any sick butterflies you've raised. (For what it's worth, I have not had to destroy a sick butterfly yet. Mine have all been OE-free.)

Step 2: Gather Your Equipment

THE BASICS

You will need:

microscope with minimum 200x magnification—Some people believe a magnification of 40x to 50x is sufficient for determining whether a butterfly is infected with OE, but I prefer much greater magnification, so I can feel more confident that my butterflies are OE-free.
surgical gloves—For handling your butterfly during testing.
plastic container and monarch egg(s)—You will hatch your monarch egg(s) inside in this container. (Information on finding monarch eggs is in Step 4 of this Instructable.)
tulle fabric—This is what you will use to enclose one or more of your outdoor milkweed plants, so various predators cannot get at your monarch caterpillars.
scissors—For cutting your tulle to the right size.
twist-ties (or small clamps)—For securing the tulle to your tomato cages or sections of wire fencing.
paint brush—One of the most delicate aspects of this endeavor is moving your tiny first instar caterpillars from your indoor hatchery to one of your protected, outdoor milkweed plants. A very small paintbrush and a steady hand do the trick.
clear, single-sided "Scotch" or similar tape (not the "frosted" kind)—You'll need this when it's time to test individual butterflies for OE.
index card(s)—White or light-colored. After you've finished testing a butterfly for OE, you'll adhere your Scotch tape sample to a section of the index card for record-keeping.
glass slides—Used along with the clear tape and your microscope to test individual butterflies for OE.
common milkweed plants in large pots outdoors or planted outside in the ground—See Step 3 for details.
tomato cages or sections of wire fencing—You'll surround any milkweed plants you plan to shield from predators with tomato cages or wire fencing and then completely cover these with tulle or similar fabric.

OPTIONAL

A magnification loupe (shown as #7 in the accompanying "Equipment" image) is optional. I have found that they can be very helpful when I am on the hunt for monarch eggs. By affording me an extra close look at them, my loupe also helps me monitor the health and viability of any eggs I'm trying to hatch.

Step 3: Prepare Your Milkweed Plant(s)

GOT MILKWEED?

The monarch butterfly's host plant is milkweed, and there are many different kinds, but, as a rule, I avoid tropical milkweed varieties, because these can actually contribute to the spread of OE. You really can't go wrong with milkweed that is native to your area—I like plain-old common milkweed, Asclepias syriaca. (Here's a great resource on different types of native milkweed, if your head is spinning right about now...)

No matter what type of milkweed you decide to grow, you're going to need to grow a lot of it. Caterpillars eat a shocking amount of the stuff, and you don't want to run out. Also, ideally, you should be growing it on your own land or land you control. That way, you can be relatively certain it hasn't been sprayed with insecticides or other chemicals. I like to grow some milkweed directly in the garden and then another good amount in smaller pots that I keep outdoors.

One common mistake people who raise monarchs sometimes make is that they try to cram too many caterpillars in the same area. This promotes disease—and sometimes even cannibalism. (No one likes cannibalism, right?!) So, I try to give the caterpillars lots of room. (If one of my large milkweed plants has three or four caterpillars living on it, I likely won't add any others to it, for instance.)

Another reason to have plenty of plants? You'll want to leave some of them unwrapped/unprotected, so that adult monarchs passing by can access them to lay their eggs.

GET GOING!

Choose one of your healthiest milkweed plants. Inspect for monarch eggs or larvae first. (See "Find a Monarch Egg" section for details.) If you find any, be careful not to disturb them, while you gently hand-pick any spiders, aphids, or other insects, as well as non-monarch eggs or egg casings from the plant. (Tedious, I know...)
Next, surround your insect-free plant with a tomato cage or bit of metal fencing.
Cut enough tulle fabric to completely surround and cover the tomato cage or fencing you erected around the plant. Use twist-ties or clamps to secure the tulle. Even the top of your plant should be completely covered. Water and light should still be able to penetrate, however.
Because you will need to be able to access your protected plant occasionally, create a little "door" or flap of fabric that you can pull back as needed.
Make sure the plant cannot be accessed at the soil line by weighing down the edges of the tulle with bricks or stones. (You can also pin all the way around the base with landscape fabric pins.)

Step 4: Find a Monarch Egg and Hatch Indoors

When I first started raising monarchs, I was so obsessed that I'd catch myself staring out the window at my butterfly garden, and, the minute a monarch happened by and started messing around one of my milkweed plants, I was out the door, loupe in hand, looking to see what it had been up to. Eventually, I noticed when a female butterfly would curve its abdomen and touch the tip of itself to the underside of a leaf, that usually meant "EGG!" Each time I felt like a lottery winner.

FINDING EGGS

Monarch eggs are tiny—about the size of the head of a pin. They are pointy on the end and have ridges or stripes along their sides. (If you live in a place where they salt the roads to control icy conditions in the winter, then you may have seen those large, pointy silos along the highway where road salt is stored. Those kind of remind me of giant monarch eggs.) Anyway, as to their color, some monarch eggs are pearly white. Others look creamy-yellowish. Take a look at these great resources to see the monarch lifecycle from egg to adult:

egg
five larval stages—These are called "instars."
pupa
adult

Typically, monarchs lay their eggs toward the top portion of the milkweed plant, so look under the first few sets of leaves. I have found monarch eggs deposited on top of a leaf as well as several scattered around on top of a green seed pod, but this is much less typical.

NOTE

By the way, there are some things you'll see that look like monarch eggs but aren't. Most often, I have been fooled by bubbles of milkweed sap that have bled out and dried on the underside of a leaf. These might be the right size as a monarch egg, but often they'll be the wrong shape—too rounded. They're also bright white and almost a little shiny. If you have a magnifying loupe, it comes in especially handy for ruling out lookalikes.

HATCHING EGGS

Once you've found an egg, remove the leaf it has been deposited on and carefully place the whole leaf with egg side facing up in your plastic container. I line my container with a slightly damp paper towel to help keep the leaf moist. Keep the container out of direct sunlight and make sure the leaf doesn't dry out.

The egg should hatch in about three days at which time you'll see a really tiny monarch caterpillar. During this "first instar" stage, the caterpillar will be two to six mm long. You can provide it with a fresh milkweed leaf to snack on after it has hatched, and give it another day or two to get large enough to safely be transferred to one of your protected, outdoor plants.

Step 5: Transfer Monarch Caterpillar to Protected, Outdoor Milkweed

MOVING 1ST INSTAR CATERPILLARS

Once your first instar caterpillar has gotten at least big enough for you to see fairly easily, you should be able to transfer it to one of your protected, outdoor milkweed plants. I use a small, dry paintbrush to accomplish this. (See accompanying video.)

For best results, make the move when it isn't too windy outside. Unwrap a portion of tulle from one of your protected plants, so you can access the plant easily. Bring the caterpillar—container and all—outside by the plant, and choose the leaf you'll deposit your caterpillar on ahead of time. (By the way, you might want to bring a friend with you to be an extra pair of eyes and hands, especially the first couple of times you try this.)

When picking up a first instar-sized caterpillar, I sneak a few bristles of my paintbrush underneath it to very gently dislodge it from its leaf. They tend to attach themselves with fine, silky threads, so you may also need to move some of these out of the way. When I am certain I have the caterpillar balanced on my paintbrush, I move it to its new leaf, and touch the bristles of my paintbrush to the leaf's surface. Sometimes, the caterpillar marches onto the leaf by itself. Other times you may have to help it off the brush and onto the new leaf's surface with a slight twisting motion of your paintbrush.

Before you let go of the new leaf, make sure the tiny caterpillar has a chance to stick itself to the new surface. It will likely begin moving to the underside of the leaf, once it has its bearings. When you are certain the transfer is complete and it's safe to let go of the new leaf, it's time to carefully wrap the protected plant back up.

ONGOING CARE AND FEEDING

Make sure your milkweed plants get enough water and periodically check to see that caterpillar(s) on your protected plant(s) still have plenty to eat. Caterpillars will grow in size along this schedule:

1st instar = 2 to 6 mm, one to three days
2nd instar = 6 to 9 mm, one to three days
3rd instar = 10 to 14 mm, one to three days
4th instar = 13 to 25 mm, one to three days
5th instar= 25 to 45 mm, three to five days

Step 6: (Optional) Move 5th Instar Monarch Caterpillar to Outdoor Cage

Fifth instar caterpillars have a tendency to want to wander off when it's time to form their chrysalides. As long as your protected plants are really secure, your fifth instars should stay put. They'll most likely attach themselves to the top portion of your protective netting or, possibly, to part of your fencing.

I have made this step optional, but, if you are able to do so, I do recommend moving your 5th instar caterpillar(s) to a protected cage that, again, will be kept outside. I have a couple of cages like this that I use just for this purpose. When my 5th instars are fully grown and nearly ready to form chrysalides, I'll move them from one of my outdoor protected plants to the inside of one of my wooden cages. I also include one of my smaller, potted milkweed plants just in case they still have an appetite. Usually, though, it doesn't take long before they climb off the plant and attach themselves to the ceiling of the cage. They hang in what's called "J formation" for a day or so, and then they shed their caterpillar stripes one last time to reveal sparkly, green chrysalides.

(Incidentally, one of the creepiest, most amazing things you may ever see is a monarch going from the fifth instar caterpillar stage to the chrysalis stage. See accompanying video.)

When the last 5th instar caterpillar has moved off of my potted milkweed plant, I remove the plant from inside my wooden cage, water it, and give it time to regrow its leaves.

Step 7: Monitor Chrysalis and Watch for Eclosure

WHAT TO EXPECT

It takes anywhere from seven to 13 days for most chrysalides to reveal the adult monarchs within. In part, this depends on the temperature outside. I've noticed this process takes longer in cooler weather. (If you've never seen this take place, have a look at the accompanying video. It is pretty amazing!)

Over time, the chrysalis will change from green to black. Eventually, you'll be able to see the adult butterfly through the chrysalis, and, not long after, the adult butterfly should emerge (or eclose.) When the butterfly does emerge, you'll notice its body is huge compared to its wrinkled, shrunken wings. This is normal, and the butterfly will redistribute liquid from its swollen abdomen to fill out its wings. About half an hour after eclosure, the butterfly will excrete a rusty-looking liquid called meconium. This is normal, too.

It takes at least two hours for the butterflies wings to take shape and dry out. Don't move on to the next step—testing your butterfly for OE—until its wings are completely dry.

NOTE

If the butterfly has trouble emerging from the chrysalis, it might be sick. Also, if your butterfly falls onto the ground (or the floor of your optional 5th instar cage), let it climb onto your finger and help it back up, so that it can hang properly to finish filling out and drying its wings. If it falls a second time, there is likely something wrong with it.

Step 8: Test Adult Monarch(s) for OE

So, your butterfly successfully eclosed and its wings are nice and dry? Then you're ready for the next step—testing it for OE. Grab a friend to be an extra pair of hands as needed and follow these steps:

Make sure your glass microscope slide is clean and dry.
Tear off a small section of clear tape. I typically use a length of about half an inch.
Put one surgical glove on the hand you'll use to hold the butterfly.
Open your cage or uncover your protected plant to afford access to the butterfly. Position your index finger such that the butterfly can climb onto your finger. Be gentle but firm, keeping the butterfly's wings closed at all times. Tilt the butterfly back to expose its abdomen. (See accompanying graphic for reference.)
Taking special care that the tape does not make contact with the butterfly's delicate legs, use your non-gloved hand to press your section of clear tape against the lower portion of the butterfly's abdomen. You will remove some scales from the butterfly, but this will not affect its ability to fly or function.
Stick the tape down in the center of the glass slide, and put the butterfly back into its enclosure for the time being.
Examine the slide under your microscope at 200x magnification. Again, see accompanying graphic for reference. The slide pictured at lower left shows the scales from a healthy butterfly. The slide to its right comes from http://monarchparasites.uga.edu and shows an OE-infected monarch's scales. OE spores are smaller than the butterfly's scales and they look slightly lemon-shaped.
When you've determined whether or not your butterfly is healthy, remove the tape from your slide and affix it to one of your index cards. Label with the date, whether or not the sample was OE-free, and any other notes you wish to add.
Discard your glove and disinfect the slide and any other surfaces and tools the butterfly sample may have come into contact with with a weak bleach solution.
Finally, if your butterfly is infected with OE, you must not release it. Doing so will just make things worse for all the healthy monarchs out there. Place the infected butterfly in an envelope and place it in the freezer for a couple of hours. This will euthanize the insect.

Step 9: Release (If Your Butterfly Is Healthy!)

If you made it to this step, your butterfly must have passed its OE test with flying colors. (Pun intended!)

If it's late in the evening or rainy outside, don't release your butterfly yet. It will be OK hanging out in your protected enclosure overnight. During inclement weather I had four butterflies waiting in the wings once. (See what I did there? Again!!)

WHEN IT'S TIME TO GO. . .

When it is time to send your butterfly on its way, put it in a sunny spot, so that it can warm up and get acclimated. I like to place mine high up on nectar-producing flowers, just in case it wants to feed right away. (See accompanying image.) I also like to hang out nearby and make sure it eventually flaps away.

Step 10: (Optional) Geek Out on Further Reading and Resources

There is so much to know about monarch butterflies and how to raise them—I've just barely scratched the surface. Here are some extra resources and academic papers you might find useful:

Monarch Joint Venture | University of Minnesota. “Rearing Monarchs Responsibly.”
Altizer, Sonia, and Jaap de Roode. "When butterflies get bugs: the ABCs of lepidopteran disease."American Butterflies 18.2 (2010): 16-27.
Borders, Brianna, Casey, Allen, Row, John M., and Wynia, Rich, et.al. “Pollinator Plants of the Central United States: Native Milkweeds.” The Xerces Society for Invertebrate Conservation (2013): 1-21.
Davis, Andrew K., and Lee A. Dyer. "Long-Term Trends in Eastern North American Monarch Butterflies: A Collection of Studies Focusing on Spring, Summer, and Fall Dynamics."Annals of the Entomological Society of America (2015): sav070.
Lindsey, E., Mehta, M., Dhulipala, V., Oberhauser, K., & Altizer, S. (2009). "Crowding and disease:effects of host density on response to infection in a butterfly–parasite interaction."Ecological Entomology, 34(5), 551-561.
Pleasants, John M., and Karen S. Oberhauser. "Milkweed loss in agricultural fields because of herbicide use: effect on the monarch butterfly population."Insect Conservation and Diversity 6.2 (2013): 135-144.
Nail, Kelly R., Carl Stenoien, and Karen S. Oberhauser. "Immature monarch survival: Effects of site characteristics, density, and time." Annals of the Entomological Society of America 108.5 (2015): 680-690.
Prysby, Michelle D., and K. Oberhauser. "Temporal and geographic variation in monarch densities: citizen scientists document monarch population patterns." The Monarch Butterfly: Biology and Conservation (2004).

There are also a number of great informational websites and Citizen Science projects you may be able to take part in, including:

THANK YOU!

Last but not least, thanks go to my friends Michael and Mohammed for taking some photos for me while I had my hands full and to my dad, too. He also helped with photos and he has filled his side yard with enough milkweed to support a whole army of monarchs!