To Rear . . . or Not to Rear? The Monarch Question
Photo by Michelle Berry Lane, 2017
The Monarch's size, and its brilliant orange and black coloring stands out in our landscape. Their beauty is reason enough to enjoy seeing them, but we have also come to care for them even more because their survival is threatened. As we've learned about their need for milkweeds, more and more people are planting it in their landscapes.
The Eastern Monarch is unique among butterflies because of its lengthy, annual migration of thousands of miles to the Sierra Madre mountain range in Mexico. This amazing annual journey of the Monarch has elevated it to an iconic status.
What the Monarch Needs to Find its Way to Mexico
The migratory cycle of this species takes place over many generations in one year, so that those who migrate south are 3-5 generations removed from those who overwintered in Mexico. Throughout each generation, healthy wild caterpillars develop with these important environmental cues in place:
- changes in the length of day period
- location of the sun
- temperature fluctuations
- air currents
- and possibly electromagnetic cues
The last generation of caterpillars that live to emerge here in southeast Michigan as butterflies in the fall, will be ready use those cues to find their way to Mexico.
What is the Current Status of the Monarch Butterfly Population?
The Eastern Monarch butterfly has been internationally identified as endangered off and on by the IUCN over the last few years, and it is now listed as "vulnerable". Our own US Fish and Wildlife Service is actively seeking for it to be listed under the Endangered Species Act as "Threatened", but this designation has been tabled.
Recent reports that the population of Eastern Monarchs doubled this year as compared to last year, are definitely worth celebrating. However, relative to historical numbers, they are still dangerously low, and significantly lower than most over the last ten years. See the image below from The Monarch Joint Venture: 
Public awareness and concern about the decline of the Monarchs over the last 3 decades, has grown. This concern galvanizes many to want to do something to help.
There are several things you can do. The easiest and most effective way that you can help the Monarchs is to increase habitat by planting native milkweed plants, which are larval hosts for the Monarch. They cannot survive without ample milkweed to lay their eggs on. It is the ONLY food the caterpillars can eat.
Equally important is to stop using herbicides and pesticides, or at least reduce them significantly, in our landscapes, both private and public. Herbicides kill milkweed, and insecticides, particularly anything that contains neonicitinoids, will kill the Monarch at all stages of its lifecycle. They also kill many other, even more important pollinators, like native bees that support our ecosystem.
Captive rearing of Monarchs, from egg to adult, has been another strategy, that also builds our relationship with this beautiful butterfly, but if we're not careful, we can do more harm than good.
The hope behind collecting eggs and rearing the caterpillars until they become adult butterflies, is that we are giving them a better chance to survive by removing them from potential predators and weather events that challenge their survival. This strategy also deepens our affection and appreciation for the insect as we care for it and watch it grow. We are more likely to want to save a creature we love.
The intention behind captive rearing is wonderful, but there are some methods that actually cause harm, even when we feel we are taking good care of them. What follows is an brief overview of methods, leading up to the BEST practice for rearing Monarchs.
- Commercial Captive Rearing: generally done indoors, sometimes outside. Reared for the purpose of educational use or commercial use. These are eggs you can buy and raise. Problems occur in these dense populations, such as disease spread and the formation of new disease mutations that are harder for wild populations to fight. Indoor captivity also impacts development negatively.
BENEFIT: None.
PROBLEMS: This practice can cause harm and will not help increase the population of butterflies who survive or can migrate. Butterflies reared from commercially produced eggs should never be released into the wild. -
Wild Captive Rearing - Indoors: Collecting the eggs from the wild, and then placing them in an indoor habitat with milkweed to continue their life cycle, then releasing the adult butterflies after they emerge.
BENEFITS: safe from predators and weather events; developing affection for the insect.
PROBLEMS: Rearing indoors separates the caterpillars from the environmental cues that help them to survive and find their migratory path to Mexico. Indoor rearing is potentially harmful.
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Wild Captive Rearing - Outdoors: Collecting the eggs from the wild, and placing them into an outdoor, screened enclosure. The enclosure should be weighted with a brick or large rock so they cannot fall over.
BENEFITS: The caterpillars hatch and grow in the conditions that nature provides, with developmental cues that prepare them for migration if they are the last brood of the fall. They are sheltered from predators.
PROBLEMS: Overcrowded cages are unhealthy. Milkweed must be kept fresh and plentiful, never just single leaves lying on the bottom, but plant stems standing tall and well watered as in nature.
One last concern: Bringing in every egg you find might also be harmful. It is tempting and feels good to raise them as a measure that mediates the harm that we have caused. But ultimately, these are wild creatures and their best lives are ultimately lived in the wild.
In the wild, they never experience crowded conditions as caterpillars. When the eggs are laid by a female, she deposits each one on its own milkweed leaf, ensuring that there will be a little competition from other hungry caterpillars for food.
Simultaneously rearing many together at the same time in the same enclosure endangers their survival because crowded conditions spread disease. Large caterpillars also sometimes eat the smaller ones. You may be unintentionally doing more harm than good.
The best practice for rearing Monarch caterpillars is to rear them in a clean, uncrowded, screened enclosure, outside, so they can develop in the conditions they are meant to thrive in.
If you want to raise a caterpillar, you can purchase a small, zippered screen "house" for your caterpillar to grow in. There are lots of them available online. The main thing is to make sure it has enough space to accommodate the milkweed cuttings and the caterpillar's need to find a place to go when it is big enough to pupate and emerge as a chrysalis. We recommend at least 24" high.
You can also easily make an inexpensive enclosure with an inverted metal tomato cage, like the image above.
- a clean metal tomato cage (can be used but not too rusty)
- a yard of cheap netting from a craft or fabric store
- metal pizza pan from the dollar store
- needle and thread
- 6-8 clothes pins
How to do it:
- The metal "roots" that would have gone into the ground, become the ceiling support for the top of the cage. Bend them inward, and cover the whole thing with netting.
- Knot the end of the netting at the top, and whip-stitch the bottom edge around the ring at the base. clothes pins keep the edges closed.
- Set the base into the pizza pan. Use clothespins to secure it on the pan.
- Paper towels or newspaper in the bottom make it easy to clean.
- Before you attempt to rear any caterpillars, make sure you have plenty of milkweed plants to harvest.
- Cut your milkweed plant so that there are several rows of leaves growing from the central stem.
- Keep it watered. Use an old butter tub or other plastic container with a lid to hold it upright. Make an "X" in the top with a knife, fill it with water and put the lid on. Place it in the cage.
- Make a vertical cut in the base of milkweed's cut stem--this increases hydration and keeps the milkweed healthier for the caterpillars. Push the stem into the "X" cut in the container top.
Rose/Swamp Milkweed (Asclepius incarnata)
Migratory Monarch butterflies, clinging to the branches of oyamel fir trees in the Sierra Madre mountains of Mexico
Please remember that the most important way to help is to provide healthy, pesticide-free landscapes, filled with an abundance of native milkweed plants, the way it was before we were here.
Rearing Monarch caterpillars and then releasing a healthy adult butterfly into the wild, when done in a way that respects the natural needs of the wild caterpillars, is a thrilling and beautiful experience. We care more about the creatures we come to know well.
💚Keep Planting!💚
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If you would like a deeper dive into this topic, here are few more articles:
- Everything You Need to Know About Eastern Monarchs and How to Help Them (Xerces Society)
- Contemporary loss of migration in monarch butterflies research study about the importance of environmental cues in Monarch migration (University of Chicago, 2019)
- Excellent video: Raising Monarchs - Captive Rearing And Migration (Help The Monarch Butterfly) by MrLundScience 2019
| by Michelle Berry Lane, 2025 |