Learning that raising monarch caterpillars might aid this remarkable species against threats from habitat destruction and pesticides, I decided to try it myself. At the very bottom of this long post is REARING MONARCH BUTTERFLIES IN BRIEF.
I had already seen monarch butterflies lay eggs, and knew to watch for a monarch to land on the top of a milkweed leaf, bending her abdomen beneath. I had also come to recognize the oval, pale yellow eggs that stood out singly from the underside of a milkweed leaf.
A butterfly I watched lay two eggs on July 2 got me started. Parasites and diseases are able to attack even very young caterpillars, so I decided to chance bringing the eggs indoors rather than tracking their hatching in place. I brought the leaves in and laid them upside down in a saucer with just enough water beneath the leaves to prevent them from wilting. The saucer was mostly kept out of direct sunlight. Each day I made sure the leaves weren't drying out.
Four days later on the 6th, both eggs had hatched and the caterpillars were already doing visible damage to their leaves. They grew almost as I watched, and at the end of that day I transferred them to a cut milkweed plant:
Raising monarchs this way, on separate free-standing plants with no container, I had no caterpillar mortality, other than a couple that wandered. One caterpillar died right after birth, having hatched from an egg I accidentally handled. One pupating monarch died. Otherwise, no mortality at any stage.
Even as the first caterpillars were growing big enough, I thought, to win an arm-wrestling contest, I saw another monarch laying eggs, and soon had more leaves on new saucers. This time, I was able to watch and photograph the hatching of three tiny caterpillars. Each one, within a minute or so of emerging, turned around and began eating the egg shell it had just emerged from. After that, they went to work on the tiny leaf hairs, and then the leaf itself.
Caterpillars produce frass (poop) that becomes larger and more copious as they grow. I found that it was enough to keep a sheet of newspaper underneath each plant, and begin changing it occasionally as the caterpillars got big.
Only when caterpillars neared their full size was it necessary to put their plant into the up-ended aquarium tank and close the opening with a screen: the fifth instar--the last stage of these caterpillars--begin to go walkabout in a bid to find a good place to become a chrysalis; I didn't want to lose track of them in a house with many pairs of feet walking around and also two curious dogs.
Stages in the life of a monarch (with the assistance of Adam and Eve, and Athos, Porthos, Aramis and D'Artagnan (the first two cohorts).
Two weeks later, the kids have molted twice, and are now "third instars." After another molt, the tentacles will be markedly longer, and will be more useful as feelers.
The shed skin is anchored to the leaf with silk. Empty prolegs and true legs are still visible.
A pale face marks a recent molt.
Over a few weeks, a caterpillar grows hundreds of times bigger. For comparison, here is a second instar compared to a 5th instar--Adam, one of the first pair we raised. (Guess what the other 5th instar's name is?) Black bands are wider, giving a darker cast to 5th instars.
On their plant in the tank, Adam and Eve at work upon the same leaf.
At the start of the video, the caterpillar has been a J since yesterday,
its feelers shriveled as it became ready to shed its skin about an hour ago,
and the J has just begun to relax for the big push.
Metamorphosis and Emergence
*Peak migration here at 41 degrees north latitude is mid-September.
I had already seen monarch butterflies lay eggs, and knew to watch for a monarch to land on the top of a milkweed leaf, bending her abdomen beneath. I had also come to recognize the oval, pale yellow eggs that stood out singly from the underside of a milkweed leaf.
A butterfly I watched lay two eggs on July 2 got me started. Parasites and diseases are able to attack even very young caterpillars, so I decided to chance bringing the eggs indoors rather than tracking their hatching in place. I brought the leaves in and laid them upside down in a saucer with just enough water beneath the leaves to prevent them from wilting. The saucer was mostly kept out of direct sunlight. Each day I made sure the leaves weren't drying out.
Four days later on the 6th, both eggs had hatched and the caterpillars were already doing visible damage to their leaves. They grew almost as I watched, and at the end of that day I transferred them to a cut milkweed plant:
- I found a plant small enough to fit nicely in my up-ended aquarium tank, used a garden hose to spray the undersides of the leaves to remove most other insects and aphids, and stood the stem up in water in a disposable coffee cup with the lid on and the stem inserted through the straw hole. (Putting the plant into the aquarium tank turned out to be unnecessary: the caterpillars stay on the plant and often even on the same leaf until they are quite large.)
- Because the caterpillars were too tiny to handle safely, I used scissors to cut out the bit of leaf they were on, and put these leaf fragments upside down on leaves of the new plant. (Having the leaf fragments upside down meant the caterpillars were sort of sandwiched between, and seemed to speed up the transfer, since they were already in contact with the new plant.)
Raising monarchs this way, on separate free-standing plants with no container, I had no caterpillar mortality, other than a couple that wandered. One caterpillar died right after birth, having hatched from an egg I accidentally handled. One pupating monarch died. Otherwise, no mortality at any stage.
Even as the first caterpillars were growing big enough, I thought, to win an arm-wrestling contest, I saw another monarch laying eggs, and soon had more leaves on new saucers. This time, I was able to watch and photograph the hatching of three tiny caterpillars. Each one, within a minute or so of emerging, turned around and began eating the egg shell it had just emerged from. After that, they went to work on the tiny leaf hairs, and then the leaf itself.
I had read that a monarch caterpillar will sometimes eat a smaller caterpillar--perhaps simply because it is "in the way." So I always kept young caterpillars on different leaves far apart on the same plant, and never put very young caterpillars on the same plant as older caterpillars.
Caterpillars produce frass (poop) that becomes larger and more copious as they grow. I found that it was enough to keep a sheet of newspaper underneath each plant, and begin changing it occasionally as the caterpillars got big.
Only when caterpillars neared their full size was it necessary to put their plant into the up-ended aquarium tank and close the opening with a screen: the fifth instar--the last stage of these caterpillars--begin to go walkabout in a bid to find a good place to become a chrysalis; I didn't want to lose track of them in a house with many pairs of feet walking around and also two curious dogs.
Stages in the life of a monarch (with the assistance of Adam and Eve, and Athos, Porthos, Aramis and D'Artagnan (the first two cohorts).
Athos' egg. The aphid upper right kindly agreed to provide scale.
Athos emerges just before midnight. Four or five minutes later he is at work
eating the eggshell. He will be at it for half an hour.
Then it's off to tour the neighborhood.
While Athos munches, Porthos' egg shows the dark head of a caterpillar
that is within hours of emerging. The eggs are beautiful things.
that is within hours of emerging. The eggs are beautiful things.
By mid-morning, Porthos had emerged and was at work on his leaf.
By noon, Aramis and D'Artagnon are both preparing to hatch.
Early that evening, Aramis has emerged.
Deciding to make an entrance, D'Artagnan waited until prime time.
D'Artagnan makes his entrance.
He sets about his first meal. He isn't one to clean his plate.
D'Artagnan sets about his first meal.
Athos has not been idle; the circle of damage (not always penetrating through the leaf) is characteristic of that made by early first instar monarchs. Already he has grown.
Aramis did not finish his egg either, but has begun
a meal of leaf trichomes (the fuzz on the underside).
Porthos is not far behind Athos.
Artemis' egg was on a leaf that was dying; he transferred
to a fresh leaf and is beginning to find his way.
Before long, he's figured out that fuzzy stuff is tasty.
Eventually he goes on to the leaf itself.
By the next day, all are merrily munching, and Athos has developed some real color--
but only black. At this point, all are "first instars": after growing they will shed
their skins to become second instars. As caterpillars, they will go through 5 instar stages.
but only black. At this point, all are "first instars": after growing they will shed
their skins to become second instars. As caterpillars, they will go through 5 instar stages.
The milky sap you see is the milkweed's defense against herbivores: it contains a cardiac glycoside that is poisonous to many animals. Monarchs have adapted not only to eat it without harm, but also to concentrate it in their own bodies so that larger predators (chiefly birds) learn to avoid eating them--associating their bright colors with the bad taste. This is likely the reason monarchs caterpillars became restricted to eating only milkweed. (The butterflies are happy to drink nectar from a variety of flowers.)
Each molt (called ecdysis) follows a time of inactivity. It happens in just a few minutes so is easy to miss, but you might see the shed skin before the caterpillar eats it. (What better food? Your own skin has just the balance of raw materials needed to grow!) Even if you don't find the shed skin, the pale head stripes gray rather than black) is a clue that a monarch has just molted.
Fifth instars eat voraciously, and are big enough to demolish an entire leaf in less than a day. They need to be in a container like an up-ended aquarium tank since they are prone to wander, looking for a good place to pupate.
(No, I don't know which is which; male and female caterpillars look alike, anyway.)
Fifth instars will pupate (after forming their chrysalis) pretty much any place they can hang free. We encouraged ours to pupate on the underside of milkweed leaves, where they invariably anchored their silk pads to the strong midvein. (One minor problem we had was plants dying or wilting before the butterflies emerged. Some leaves ended up held to their stems by masking tape, so their chrysalises would be safe.) But other surfaces would do: several caterpillars began making silk pads on the glass inside the aquarium tank, and I allowed one to pupate there without trouble.
Technically, the caterpillar is the larval stage of the butterfly (just as a maggot is the larva of a housefly), while the chrysalis is the pupa.
A few days before it pupates, you may notice a greenish tint to the white parts of the skin: this is probably the color of the soon-to-be pupa shining through. If you haven't already, this would be a good time to put the critter on its milkweed into an enclosure.
You will notice a caterpillar waving its front end back and forth over one place as it lays down nearly invisible silk, then it will reverse its body to be head downward and anchor its hind end in the silk with a sort of spike. In short order, the caterpillar relaxes, hangs, and then curves its body into a "J." Within about a day, it will form its chrysalis.
You can just see the white silk this caterpillar is putting on the midvein of this leaf. (The silk glands are in its head.) It will attach itself to the silk to form a chrysalis like that in the background.
The formation of the chrysalis presents a mystery: it is shaped and proportioned very differently from the caterpillar--yet also differently from the butterfly it will become. The process of formation is fascinating to watch, as the J-shaped caterpillar goes through convulsions and contractions that cause the final caterpillar skin to be shed, then contorts itself into its chrysalis shape, before the final skin hardens.
In only a half-hour, Adam went from the above, to the below.
Forming a Chrysalis
About a day after anchoring to its silk pad and forming a J, the caterpillar begins to convulse, the hind end begins to contract, and during this time the caterpillar sheds its skin. The skin splits at the outside of the curve of the J, and the skin migrates upward until it falls off the hind end. (This final skin falls directly beneath the chrysalis.) The creature's front end appears already to have the shape of folded wings. The back end, still rather caterpillar-like, contracts and contracts until it shortens into the tiny dome-shape of the top of the chrysalis. Due to the contraction of the abdomen, a dark band perhaps a third of the way back from the head ends up near the top of the chrysalis, and becomes a very attractive black-and-gold after the chrysalis skin hardens. After that, enormous changes begin which are invisible from the outside.
its feelers shriveled as it became ready to shed its skin about an hour ago,
and the J has just begun to relax for the big push.
Metamorphosis and Emergence
Inside the chrysalis, the caterpillar is simply gone--having dissolved itself into nutrient-rich soup. Islands of cells survive that already began to develop into adult structures before the caterpillar began to pupate. These cells divide rapidly by using the "soup" as food, and mature into the adult butterfly over a period of 8-12 days.
Only on the last day will the chrysalis darken as the butterfly begins to develop its adult colors; first a faint tracery of wing veins appears, then some of the orange of the wings, and then the rest of animal goes dark. Within about 24 hours the butterfly will emerge, but emergence itself takes only seconds. After tumbling from the split chrysalis and righting itself, the new butterfly will gradually pump its wings to full size and smooth out the wrinkles. In a few hours the butterfly is airworthy, and can take its first unsteady flight, until shortly becoming a confident flyer.
Only on the last day will the chrysalis darken as the butterfly begins to develop its adult colors; first a faint tracery of wing veins appears, then some of the orange of the wings, and then the rest of animal goes dark. Within about 24 hours the butterfly will emerge, but emergence itself takes only seconds. After tumbling from the split chrysalis and righting itself, the new butterfly will gradually pump its wings to full size and smooth out the wrinkles. In a few hours the butterfly is airworthy, and can take its first unsteady flight, until shortly becoming a confident flyer.
Emergence is very soon.
Only moments after emergence, wings are rumpled and abdomen--
telescoped to fit into chrysalis--is still fat and short.
These butterflies--siblings, I recall--emerged within minutes of each other.
On the left is a female, on the right a male. (The black spot on a vein of each hind wing
produces pheromones that attract females.) The male emerged earlier, so is farther along.
Butterfly emerges only in the last two minutes--just after focus goes all blurry!
Two minutes after emergence, she begins to inflate her wings. If adult insects have six legs,
why do I only see four? The forelegs are small and kept curled up.
Wings and abdomen take adult shape. She exercises the proboscis
that will allow her to feed on nectar deep in flowers.
A close-up of the fuzzy palps in action.
Flexing wings in preparation.
Knowing who your friends are.
Ready for launch.
Tips for Raising Monarchs
1. Monarch caterpillars face much danger--probably mainly from insect predators, but also from parasites and disease. I often found eggs, sometimes found 1st instars, but almost never found older caterpillars. Even though many eggs were laid than I collected (judging from leaves with monarch caterpillar damage), none in my yard this year reached adulthood without my assistance.
2. You need a ready source of milkweed--to collect eggs, and feed caterpillars. There may be some in a weedy area near your home. Otherwise, plant some! (I planted mine in my native garden many years ago, with no thought of monarchs. I now have more plants than I know what to do with.) Decline in milkweeds is the chief problem monarchs butterflies face right now.
3. The easiest way to find eggs is to watch the butterflies lay them. The female lands near the edge of a leaf, bends her abdomen beneath the leaf, and then flies off. Laying the single egg takes only seconds. She might well flutter around seemingly aimlessly laying more if you watch. I often collected several eggs laid by the same mother. Once you've seen a few eggs, you will get good at searching for them. But that's more work.
4. Pinch the leaf off the plant being careful not to disturb the egg. Lay the leaf in a saucer with a tiny bit of water to prevent the leaf drying out before the egg hatches. (Add a few more drops of water every day.) I often had two or three leaves in the same saucer. If the leaf dies, move the caterpillar to a fresh one soon after it is born.
5. The tip of an egg turns dark (the head develops color) less than a day before it hatches. Once hatched, the 1st instar can work on that leaf (if healthy) for at least a day. However I had a few caterpillars wander, and one drowned in the tiny bit of water in the saucer, so I try to keep an eye on the newborns. If you have to leave them unattended--or when you think it's time--place the leaf with newborn on a plant. It may take awhile, but the caterpillar will eventually move on to the plant.
6. Milkweed plants can be cut with scissors and placed in cups of water with lids--iced coffee cups and perforated lids are ideal. (If you are careful, a coffee can lid with hole cut in the center can substitute.) Cut only a straight plant so it won't fall over, and put the stem all the way to the bottom. Fill full of water for stability.
7. In the beginning, I used a hose to wash aphids, etc., off the plants before I brought them in, but eventually I stopped bothering. It didn't seem to matter. Also, I sometimes found "volunteer" monarch caterpillars on the plants.
8. Most milkweed plants will live for days or even weeks in water, but some will wilt almost immediately. If this happens, get a fresh plant and transfer all your caterpillars. The safest way to transfer them is to pinch leaves off the old plant and put these on the new. Be careful they don't fall off.
9. For the most part, caterpillars stay on their plants, though they often move from leaf to leaf. Only a few times did a caterpillar go missing from its plant, and I usually found them before they got far.
10. Increasing amounts of larger and larger frass (poop) means thinking ahead about how to clean up. I put several sheets of newspaper under my plants.
11. Several caterpillars can occupy the same plant if they do not differ much in size. But do not allow a plant to become denuded: if food is becoming scarce, even smaller caterpillars will wander off to search for more.
12. As they become large, a few caterpillars can demolish an entire plant in a few days.
13. A caterpillar that hasn't moved for an entire day is probably about to molt. Leave it alone. In general, I tried not to handle the caterpillars at all, fearing to harm them. At most, I might coax an errant caterpillar onto my finger to restore him to a plant.
14. The fifth instars have more black than the earlier ones, and can approach two inches long. These eating machines need to be in a container with their plants, lest they wander. I had a small aquarium tank I stood on end, and cut plants to fit in. A screen closed the open side, and saved many caterpillars from being lost. (Once they J, they no longer need to be contained.)
15. A chrysalis should be disturbed as little as possible. In general, from the time a 5th instar formed a J 'til after emergence, I did not move them any more than absolutely necessary. If a chrysalis (or the leaf it is on) falls, use a bit of tape to hang it back up so that it is properly oriented. One of our plants wilted right after caterpillars had J'ed, and we ended up taping the leaves to the plant.
16. It takes from a few hours up to a full day for a new butterfly to go on its way. For that reason, I didn't worry much about containing a plant that had chrysalises on it: they wouldn't wander off if they emerged when I wasn't watching. On the other hand, if you have a dark chrysalis and need to go away, put the plant outdoors under shelter while you're gone.
17. If your butterflies launch in the summer, you are building up the local population. But if you are still launching as fall approaches, you may be helping to raise the generation that will head south on an amazing, multigenerational migration.* Either way, well done!
Two excellent and detailed resources are Monarch Lab and Monarch Watch.
REARING MONARCHS IN BRIEF
1. Get a source of milkweed. (Grow some!)
2. Collect eggs by watching butterflies lay them, or checking under leaves. Eggs hatch after about 4 days.
3. Raise caterpillars on whole milkweed plants standing in soft drink cups of water with snap-on lids. Caterpillars mostly keep to their plant so cage is necessary until caterpillars become big. Put paper under plants to catch frass.
4. If a plant wilts, best to replace it. Replace plants before caterpillars have eaten most of it. Transfer caterpillars by pinching off leaves and putting them on the new plant. Older caterpillars can be handled with care, but newly-molted caterpillars (heads are pale) should not be.
5. Big caterpillars make a lot of wet frass--replace paper often.
6. Big caterpillars begin traveling to find a place to pupate. When they get large, put them in a well-ventilated container (up-ended aquarium with screen lid) so they don't get lost.
7. Chrysalis must hang correctly oriented--don't disturb them or let them fall if you can help it.
8. The eggs hatch in about 4 days, the caterpillar (larval) stage lasts 2-3 weeks, the chrysalis (pupal) stage lasts 8-12 days, and newly-emerged butterflies are air-worthy in a day or less, so your minimum time commitment is about a month.
REARING MONARCHS IN BRIEF
1. Get a source of milkweed. (Grow some!)
2. Collect eggs by watching butterflies lay them, or checking under leaves. Eggs hatch after about 4 days.
3. Raise caterpillars on whole milkweed plants standing in soft drink cups of water with snap-on lids. Caterpillars mostly keep to their plant so cage is necessary until caterpillars become big. Put paper under plants to catch frass.
4. If a plant wilts, best to replace it. Replace plants before caterpillars have eaten most of it. Transfer caterpillars by pinching off leaves and putting them on the new plant. Older caterpillars can be handled with care, but newly-molted caterpillars (heads are pale) should not be.
5. Big caterpillars make a lot of wet frass--replace paper often.
6. Big caterpillars begin traveling to find a place to pupate. When they get large, put them in a well-ventilated container (up-ended aquarium with screen lid) so they don't get lost.
7. Chrysalis must hang correctly oriented--don't disturb them or let them fall if you can help it.
8. The eggs hatch in about 4 days, the caterpillar (larval) stage lasts 2-3 weeks, the chrysalis (pupal) stage lasts 8-12 days, and newly-emerged butterflies are air-worthy in a day or less, so your minimum time commitment is about a month.
*Peak migration here at 41 degrees north latitude is mid-September.
