Monarch butterflies are easy to raise. In just 24 to 32 days, Monarch metamorphosis (life stages, from egg to caterpillar to pupa to adult butterfly) is completed. And no matter what your age, you will be fascinated by the process.

   To raise Monarch butterflies you will need Monarch eggs or caterpillars, healthy milkweed (Asclepias) plants, and a rearing chamber. A small aquarium with a screened lid will serve this purpose. The mesh Popups we offer on the 'Popup Cages' page are excellent for rearing caterpillars as they are predator-proof, easy to clean, and easy to store (they collapse).

   Before introducing your Monarch caterpillars into the container they will be raised in, you should sanitize the container if it was previously used for anything (or if it is dirty and should be cleaned). To sanitize, wash the container in a solution of 10% Clorox and 90% water, letting the sanitizing solution on the container for 10 minutes. Then rinse, and rinse, and rinse several more times until all of the Clorox solution is completely removed. Allow the container to dry thoroughly (preferably outdoors in full sun) before putting the caterpillars inside. The countertop or table upon which the caterpillar rearing container will sit, and any utensils that will be used in the rearing of your caterpillars, should be sanitized too.

   Common Milkweed (Asclepias syriaca), Swamp Milkweed (Asclepias incarnata), or Tropical Milkweed (Asclepias curassavica) are among the best choices to be utilized as a food source for your caterpillars. Since the caterpillars will require fresh milkweed leaves every day, your milkweed source should be near by.

   To begin your rearing project, cut a few leaves from a milkweed plant. Rinse the leaves under clean water and then wipe them dry with a paper towel. Do not put wet foliage in the cage as this could cause mold to form inside the cage. Wash your hands after handling milkweed foliage. Its sap can be harmful, especially if it comes into contact with your eyes. Put the milkweed leaves in the rearing chamber and then carefully add the Monarch caterpillars. Apply the lid so the caterpillars cannot get out.

   If you are raising Monarchs beyond early August, I highly suggest that you sanitize the milkweed leaves that are being fed to caterpillars. You'll find instruction for doing this in the next article (please scroll down).

   Replenish the caterpillars’ food supply (milkweed) daily and be sure they have an adequate supply of fresh leaves at all times. Caterpillars do not require a source of water as they get all the water they need from the foliage they consume.

Caterpillar frass (droppings, poop) should be cleaned from the rearing chamber on a daily basis to limit the chance of disease. Even in a very clean rearing environment, watch your caterpillars closely for signs of bacterial infection or virus. If any of the caterpillars look or behave abnormally, turn blackish in color or appear deflated, remove those caterpillars immediately and keep them segregated from the others. Bacterial infections and viruses can kill the infected individuals and most are highly contagious.

   Monarch caterpillars grow fast and molt (shed their skin) five times during their growth. When they are soon going to molt, they generally crawl away from the milkweed and sit still for hours (even up to a full day). Do not gather these caterpillars up and put them back on the milkweed, thinking they just wondered off and couldn't find their way back to their food. When it's time to molt, they won't be hungry, and really should not be handled. 

After reaching their full length of about 2¼” (usually 10 to 14 days after hatching from their eggs), the caterpillars stop eating again and generally crawl to the top of the rearing chamber. There each spins a silken pad to secure itself to the lid and then it hangs upside down in a J shape until the next day.

   The transformation from caterpillar to pupa (chrysalis) must be one of the most fascinating displays nature has to offer. It begins shortly after the caterpillar’s antennae begin to look zigzagged (crinkled, wrinkled). By the time the caterpillar is ready to pupate, it looks somewhat deflated. At this point though, the deflated look is normal and to be expected.

   When the transformation from caterpillar to chrysalis is complete, the chrysalis will be only about 1” long. You will wonder how a 2¼” caterpillar could fit inside such a small container. The chrysalis will be very soft at first and at this point, and should not be touched. Once it hardens, it will be jade green with a metallic gold band near the top and metallic gold dots toward the bottom.

   Motionless, the chrysalis hangs for 10 to 14 days. Inside a remarkable change is taking place though: a not-so-cute caterpillar is becoming a beautiful Monarch butterfly. The day before the Monarch emerges from its chrysalis, it turns transparent and you can actually see the Monarch’s orange and black wings inside.

   Once the chrysalis cracks open, it takes less than 30 seconds for the butterfly to completely emerge from its shell. Immediately following emergence, the Monarch’s wings are small and its body is short and plump. Within 90 minutes or so, the Monarch is full-sized and able to fly. Weather permitting, it should be set free outdoors within a few hours.

About  Raising Monarch Caterpillars on Common Milkweed in Fall: How to Sanitize Leaves

                                                                                                                                                                  by Rose Franklin

It is more difficult to raise healthy monarchs from mid August thru September than it is to raise them from early June thru mid August. This is because it becomes increasingly difficult to find common milkweed that is still healthy, nutritious, and disease-free toward fall. By late August or early September, much of the common milkweed is already heading toward dormancy, yellowing and dropping its leaves. It has little nutritional value and will likely cause the caterpillars to be malnourished.

The best place to find healthy common milkweed is in a farmer’s field or along a highway where it was mowed off earlier in the season and now has a second-growth of tender, lush, green foliage. This is prime stuff to utilize as caterpillar food. Another location where lush, green milkweed might be found is along a highway that is partially shaded by trees. Milkweed that has spent the summer in a lot of shade will generally be a lot greener and healthier than milkweed that has been growing in full sun.

No matter where you gather your milkweed from, if you are gathering it from mid August thru September, it should be sanitized before it is fed to caterpillars. By then, many milkweed leaves will be dotted with disease-causing pathogens (germs) and unless those pathogens are removed, they will be eaten by the caterpillars. Unfortunately, these disease-causing pathogens can't be seen. They are microscopic. But if these pathogens are consumed by caterpillars, they might likely cause the caterpillars to become ill. Some pathogens will even cause disease that will kill the caterpillars.

To rid the milkweed of pathogens that could cause disease in the caterpillars, the milkweed must be sanitized. To sanitize common milkweed leaves, cut the leaves from the stems. Dip them into a solution of 10% Clorox and 90% water, thoroughly covering both sides of the leaves. Let the sanitizing solution on the leaves for 2 minutes. Then rinse and rinse and rinse again in clean water. Wipe (don’t pat) the leaves dry with paper towels or a fabric softener-free cloth.

Once the leaves are dry, they are ready to be fed to the caterpillars.

Fresh leaves should be given to the caterpillars every day, with morning being the best time to replenish the food supply.

If need be (if leaves are drying out as they often do in fall), fresh leaves should be replenished in the afternoon also. You can gather extra leaves in the morning, sanitize them, rinse them, put them in a plastic bag, remove the air as best you can, and tie bag shut with a twist tie. Then put the bag of milkweed in the refrigerator until the afternoon feeding. Dry the leaves and put them into the caterpillar rearing container.

Raising Healthy Monarchs in the Classroom in Fall

Rearing Monarchs in the classroom is the same as rearing them anywhere else so the instructions above should be read thoroughly before you begin your rearing project. This means you begin by first sanitizing the rearing cage, the table or countertop where the cage is going to sit, and all utensils that might be used in raising your caterpillars.

Cleanliness is important but so too is the health of the host plant being fed to the caterpillars. We have all heard that “you are what you eat.” While this saying holds much merit for humans, it is more true for butterflies, and especially during the larval stage of development. In the case of humans, what we eat is important, but also of importance is exercise, emotional state, and level of stress. With caterpillars though, it’s all about the food; for all caterpillars do is eat. Eat and poop. Their health doesn’t depend upon how much they exercise or what they think about during the course of a day. It depends essentially upon what is entering and exiting their stomachs. 

Milkweed varies in nutritional quality based upon species and age. For teachers who are raising Monarchs in the classroom in September, the issue of milkweed age in an important consideration. If the caterpillars are being reared on Common Milkweed (Asclepias syriaca), they might well be malnourished.  How do I know this? By September, Common Milkweed is headed toward dormancy and its leaves are no longer packed with high-quality nutrients. Malnourished, the caterpillars’ immune system will be weakened and resistance to disease will be compromised. When the immune system is not strong enough to fight off the pathogens that cause bacterial, viral, parasitic, and fungal infections, disease is more prone to develop.

The best place to find healthy common milkweed is in a farmer’s field or along a highway where it was mowed off earlier in the season and now has a second-growth of tender, lush, green foliage. This is prime stuff to utilize as caterpillar food. Another location where lush, green milkweed might be found is along a highway that is partially shaded by trees. Milkweed that has spent the summer in a lot of shade will generally be a lot greener and healthier than milkweed that has been growing in full sun.  

Because the health of the caterpillar so much depends upon the health of the larval food, I suggest that if you are intending to raise Monarchs in the classroom in September, you also plan on having large, potted Tropical Milkweed (Asclepias curassavica) plants to utilize as larval food. To have large plants in September, you can either sow Tropical Milkweed seeds in May, or you can purchase small potted plants in June and then raise them to maturity. My suggestion is that you keep the plants in pots, moving them to slightly larger pots as necessary for continued root growth. The plants should be grown outdoors, preferably in full sun.

Since Tropical Milkweed does not go dormant until long after Common Milkweed does, Tropical should be the species of choice in rearing Monarch caterpillars in September. And to insure that the foliage is as nutritious as possible, the leaves should not be cut from the stems (this, because Tropical Milkweed foliage wilts quickly once cut from the plant). Instead, potted plants should be used to feed the caterpillars, replacing devoured plants with fresh, lush ones, as necessary.  

Will using Tropical Milkweed as the food plant guarantee healthy Monarchs? No. Quite frankly, it is much easier to raise Monarchs (and other butterfly species too) in June, July, and August, than it is to raise them in September. During the summer months, disease-causing pathogens, parasites, parasitoids, and predators all multiply exponentially in nature. By September, they are in the air, on plants, on adult butterflies, everywhere. With an abundance of pathogens abound, there is more chance for caterpillars to become infected.

Tropical Milkweed, because it contains more nourishment in September than Common Milkweed does, will certainly aid the caterpillars in keeping their immune systems strong. But with disease causing pathogens dramatically increased in number by September, it is difficult for the caterpillars to escape infection (unless the milkweed is sanitized to kill off the pathogens).

Glossary of Butterfly Terminology

Abdomen
The last of three sections of a butterfly’s body. The abdomen is composed of ten segments and contains the reproductive organs. Digestive and excretory functions also occur here.

Antenna (singular)
Antennae (plural)
Located on the butterfly’s head, these appendages are equipped with chemical receptors that serve the function of smelling. They also assist the butterfly in balance.

Caterpillar
Larva. The second stage in the life cycle of a butterfly.  

Chrysalis (singular)
Chrysalises, Chrysalides (plural)
Pupa. The shell that encases a caterpillar as it transforms from caterpillar to butterfly.

Cremaster
The hook-like appendage at the end of a caterpillar’s abdomen that is used to attach the caterpillar to its silk-like pad for pupation.  

Eclose
Eclosure, Eclosion
When the butterfly emerges from the chrysalis (pupa).

Egg
The first stage in the life cycle of a butterfly.  

Exoskeleton
The skin-like covering that provides support and protection for an insect’s body.  

Filaments
Fleshy antennae-like extensions at the front or rear of caterpillars which are used as sense organs.

Frass
The waste product (poop) excreted by a caterpillar (larva).  

Hemolymph
The blood-like substance of insects which is usually yellowish in color.  

Instar
The period between caterpillar molts. There are generally five instars during the larval stage.

Larva (singular)
Larvae (plural)
Caterpillar. The second stage in the life cycle of a butterfly.

Lepidoptera
The order of insects which includes butterflies and moths.

Molting
The shedding of skin. Most butterfly larvae molt five times during the larval stage of development.

Oviposit
The laying of eggs.  

Pheromone
A scent emitted by the males of some species of butterflies making him attractive to females.

Proboscis
The straw-like apparatus located on a butterfly’s head which is used for feeding (the intake of liquids). When not in use, it is coiled up under the butterfly’s head.

Prolegs
The five pair of leg-like appendages on the abdomen of a caterpillar’s body.

Pupa (singular)
Pupae (plural)
Chrysalis. The third stage in the life cycle of a butterfly. The stage in which a caterpillar transforms into a butterfly.

Pupate
The shedding of skin which occurs as a caterpillar (larva) becomes a pupa (chrysalis).

Spinneret
The organ located on the head of a caterpillar which is used for creating silk-like threads.

Spiracles
The small openings on the skin of insects through which they breathe.

Thorax
The middle portion of a butterfly’s body. Composed of three segments, the butterfly’s two pair of wings and three pair of legs are attached to the thorax.

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