Last year was my first full year raising monarch butterflies. Since the 1970s the monarch butterfly population has been declining. As the only butterfly to make a 2 way migration, the monarch butterfly can live long and go through quite a lot. Or it can have a very short uneventful life. It all depends what time during the year they come about.
Let's start with the sad facts. A monarch butterfly egg only has about a 10% chance of becoming a butterfly when left in the wild. However if those eggs are brought into a controlled environment, hatched and the caterpillars raised to a chrysalis, that changes to a 90% chance that each egg will make it to a butterfly.
That's an insane difference, isn't it?
If you guessed that is why I raise monarch butterflies, you're correct! There are lots of disease and predatory insects that affect the monarch caterpillar. Last year I lost less than 10% of my monarchs, almost all of them in the caterpillar stage. I released almost 40 healthy butterflies!
One of the other problems monarchs face is that the caterpillars only eat milkweed. It grows wild pretty much everywhere but is often perceived as a weed and most people don't want weeds growing in their yards.
Milkweed grows wild on the side of the roads which would be a good thing but many states have a mowing program and will mow it right down with no concern for the monarch caterpillars that are living on it!
Luckily the adult butterflies can feed off many different flowers, but the poor caterpillars are limited to eating milkweed.
Related reading: How to plant and grow a butterfly garden!
The lifecycle of the Monarch butterfly
The monarch butterfly lays her eggs on the leaves of the milkweed plant and only the milkweed plant. This is the only thing the caterpillar cat eat, which is kind of crazy that anything eats it because the white sap that comes out of a cut stem has the consistency and stickiness of Elmer's glue! She often lays her eggs on the underside of the leaves.
Monarch caterpillar eggs can be hard to spot as they are so small. The egg is kind of balloon shaped except it's a little bit longer at the point. It has little lines or ridges on it. It's usually found on the underside of milkweed leaves. It is tiny! It takes 4 days between when the egg is laid on the milkweed by the adult monarch butterfly and when it hatches.
When the tiny little caterpillar emerges he will eat the egg as his first meal. They can't see very well, so they pretty much just smell to find the milkweed that they like. They go through five different stages called Instars. In each stage the caterpillar gets a little bit bigger. When the caterpillar hatches out of the egg that's considered its first instar.
The caterpillar will spend all day eating milkweed (and pooping lol). After 3-4 days It will find an out of the way area to connect itself to with a little bit of silk thread and not move for a day or so. This would be the first molt that the caterpillar will undergo and when done he will just go back to the milkweed and start eating again.
He'll do this four times growing larger each time. When the monarch caterpillar first hatches it is tiny... Probably 2 cm in length. By the time it's ready to form its chrysalis, it's closer to the length of my pinky finger or 3 inches long.
Here are some pictures to show size. A day old cat compared to a fully grown cat. I would have loved to have them in the same picture, but it's not safe for the baby! As mentioned above, Monarch caterpillars cannot see well so they go mostly by smell and a big one will eat a small one by accident since it smells like milkweed.
I also don't like to touch them if I can avoid it.
When our little caterpillar friends are fully grown and looking all plump and happy they will decide to hang. The caterpillar climbs to the highest spot they can find and makes a little silk button that they attach their butt end to the ceiling. They hang like that for up to 24 hours.
After they hang upside down for a while they start to form a j shape, and then the skin will seem to split open starting from the head and working its way all the way down, or up because it's hanging upside down.
At this point the green and gold chrysalis is formed. The chrysalis will hang for about 10-14 days before it will eclose or emerge from the chrysalis. Towards the end you'll notice the whole chrysalis getting darker. When it's almost time, the shell of the chrysalis will get so thin you'll be able to make out the wings inside the chrysalis!
After eclosing, the butterfly will spend the next few hours hanging upside down. At first the butterfly is small, like the size of the chrysalis. But has he hangs upside down he starts moving his wings which pumps fluid into them and basically inflates them! It's pretty cool to watch.
How to care for monarch caterpillars
I collect both eggs and caterpillars. Basically, just go out and look under every leaf of every milkweed plant and you'll find both eggs and caterpillars! I use plastic containers to collect them in, but separate them by size pretty quickly so the small ones don't get hurt by the larger ones.
You want to keep the cats in similar sized groups as the largest ones will accidently eat the smallest ones. I use small Tupperware containers. Don't poke holes or they'll get out and you'll lose the tiny buggers! There's enough air in the container, but I do open them for a minute twice a day to let fresh air in.
You'll need to provide them with fresh milkweed every other day or when they run out. I rinse each leave in cool water and pat it dry before giving it to them, just in case there's any type of residue on it that may effect them. They do not need water, the milkweed leaves are all they need. Make sure the milkweed you feed has NOT been sprayed with pesticides or they will die.
They will also eat the green milkweed seed pods if you find them, but it makes their poop a funny color! It's perfectly safe for them though.
When a caterpillar gets to the 3rd or 4th instar I move them to a screen cage. I use a mason jar with a hole poked in the top of the lid for the milkweed. Do not leave the top open, they'll fall in.
3 large caterpillars can eat and entire milkweed plant in a day! Keeping up with them can be a bit much because of this....so make sure you have access to a large patch of milkweed before bringing the caterpillars inside! Only raise what you can feed!
Many people grow milkweed themselves. The first year growing milkweed is the hardest. After that it will self seed, plus it's perennial so each one will come back next year.
The caterpillars don't require much care except to feed them and clean out the frass daily. Frass is caterpillar poop. You want to remove it often so they don't get a bacterial infection from coming in contact with it.
Once they are in the big cage they will stay there till they become a butterfly. I have a few cages that I rotate through. Once there are several large caterpillars in the cage, I start another one for the next set.
You don't want too many because if it's overcrowded the caterpillars may crawl across (or even try to eat) the chrysalis's and this can allow bacteria into the chrysalis which will kill the butterfly before it can emerge!
One the butterflies emerge from their chrysalis I let them stay in the cage till the next morning and then I release them. Don't release too late in the day or they won't have time to find a safe place to spend the night and might get found by predators!
Problems monarch butterflies face
Monarch caterpillars face a lot of problems the 2 biggest being OE and T-fly. That stands for Tachinid fly which is a lot more difficult to pronounce than T-fly! The T-fly is one of the reasons that the monarch population is declining, because it is a predator insect.
This fly lays its eggs on the caterpillar. When the eggs hatch they burrow into the skin and the larvae grows inside the caterpillar. Eventually it gets big enough to kill the caterpillar. When the caterpillar dies, the eggs pop out then hatch starting the cycle again.
These ones I had brought in as a caterpillar and they were already infected when I picked them up. It's sad to lose a caterpillar this way, but at least now I can destroy the T-fly larvae thus breaking the cycle.
There's an infection that caterpillars can get called Ophryocystis elektroscirrha. We'll just refer to it as OE. This is an infection spread through eating tainted milkweed. An adult with the infection lands on the milkweed and leaves behind the spores that the caterpillars come in contact with when eating the milkweed. It can cause the butterfly to become deformed while forming in the chrysalis.
This infection is more common in areas that don't have a winter freeze like we do. Florida and California have a large problem with OE in fact, it's one of the reasons why it's now illegal to raise, breed, capture, contain, tag, collect monarch eggs, caterpillars, chrysalis or butterflies in California!
Many people who raise monarchs bring only eggs in the house because of OE. I understand not wanting to deal with fungal and bacterial infections but since you're bringing milkweed in the house even if you clean it properly it could possibly have something on it. I just feel that if I don't bring in every one I see, then they have only a 10% chance of making it to Chrysalis stage.
Also I feel pretty strongly about breaking the cycle of the T-fly. If I bring in already infected caterpillar in the fact is he's going to die from it no matter what. But at least if he dies in one of my cages I can destroy the T-fly larvae. So I give every caterpillar a chance!
I really like raising monarch butterflies and am in several online communities devoted to them. Each one of us raises between a few dozen and a hundred butterflies a year! I know my 40 butterflies from last year are not going to keep the monarchs from becoming endangered (they were dangerously close last year!) but there are thousands of us doing this in every state that it's allowed!
That's a lot of butterflies and it may be helping! By some counts the population has actually risen as of Jan 2023! We are all SO excited about this!
It sounds like a lot of work, but I only spend about 10 minutes twice a day for a few months in the summer taking care of the cats. It's a small price to pay to get to raise these beautiful creatures and maybe make a real difference in their population numbers!
Related reading: Want to learn more about growing food in containers? Check out all my 10 Ways to Attract bees to your Garden!
~L
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