Over the past two years I have learned a lot about raising monarchs in Missouri. When I started out (several years ago now), I put the found caterpillars in jars with a mesh covering (one per jar). But I quickly discovered how problematic that was. First, it was so difficult to clean out the jar and second, other than a stick I would include or the mesh covering, they had no options for where to hang and make their chrysalis. When they'd become a chrysalis on the mesh covering, that was the worst outcome because it was so difficult to take the covering off without damaging it.
So, I began using shoeboxes. I quickly learned that shoeboxes with attached lids were the best (put on their side so they could be tall and the original top becomes a door). I would cut out both sides, leaving enough edge for it to remain stable, and then I'd glue mesh over the giant holes. Last year, I added cardboard pieces to the top and bottom that I could easily remove to cleanout or replace if they got really gross, without having to replace entire boxes. I also began keeping more than one caterpillar in each box. There is a hazard that they will fight and kill eachother if you don't give enough milkweed or you simply put too many in together, but for the most part I've not had a problem doing this.
When I lost several caterpillars a few years ago to the tachnid fly, I began collecting caterpillars in the first instar and eggs. A word of caution: keep your caterpillars separated by size. A big caterpillar will eat an egg or first instar caterpillar. I have not had any trouble keeping caterpillars in the same box as chrysalises.
Now, when it comes to food for the monarch caterpillars (the most important and sometimes most difficult part of raising monarchs), research, trial and error has brought me some knowledge. I thought I'd be set after I bought a swamp milkweed plant (native to Missouri) several years ago. The next year it produced almost 15 shoots, but something happened (overcrowding? pushed out by other plants?) and it didn't come back again after that. Fortunately, it seeded a few other spots in my garden and I had swamp milkweed in another spot that next year. Since then, I have realized a plant really only comes back the next year and after that, it never does again.
I started saving the seeds (put a rubber band or plastic bag around a pod, then collect when it turns brown and is ready to pop open) and tried my not-so-green-thumb to get them to grow. I had kept them in the freezer, and got one of them to sprout. I also purchased seeds from a couple of other companies, but have found that any seeds more than a year old will never sprout. And I've found that keeping them in the refrigerator for longer periods (month+) is better than the freezer for short periods (3+days). When you purchase seeds, you likely won't know if they've been through the necessary winter step, so I put them through that anyway, dry and in the fridge until I'm ready to plant them. I also accidentally discovered this year that even weeks after I've tried to sow the seeds into a pot, when I dug up the soil where those seeds never grew, turning them into the soil got a couple to sprout. (In this picture, there are three varieties - the tall one is swamp milkweed, the thick leaves is common and those little spindly leaves is another variety I don't yet know as the seeds were a mix.)
When growing your milkweed, don't be afraid to cut it back before it gets huge. Make sure you keep some leaves on it, but cutting it back will actually encourage more branches and ultimately more leaves. I will cut off the top (with about 4 levels of leaves) and give the whole cut stem and leaves to the caterpillars, then enclose the rest of the plant to help foster it's ability to regenerate. If you do this late in the season, anticipate not getting any flowers and therefore no seeds.
If you have lots of milkweed, but aren't getting monarchs to flock to your garden, a hint: plant other flowering plants nearby. Last year when I had lantana right next to my milkweed, I got so many monarchs. This year my black-eyed susan's have done the trick. But be careful those other, more aggressive, plants don't choke out your milkweed. And note that once butterflies know your garden is a waystation, you'll see more monarchs in subsequent years. They remember where to find the milkweed.
I'd read that having multiple varieties is important. Well, I've finally gotten there. After over-wintering some tropical milkweed under some grow lamps last winter (of the 10 plants, only one made it... likely they were infected with a black mold that infects milkweed plants that don't die back each winter), I finally will have some tropical milkweed seeds to start for next year. And I finally managed to get some common milkweed and another variety to sprout late this summer.
Swamp milkweed is the preferred food for monarchs. They will eat any variety, but swamp is their favorite (easy to see too, as I find way more eggs on the swamp milkweed than the others). One caterpillar can decimate one swamp milkweed plant. So having others is very important. Finding the eggs is actually really easy once you know what you're looking for. They start out as small white dots then before they hatch, they turn black. Here's an egg on a swamp milkweed leaf, ready to hatch in a day or two:
Monarchs will also eat butterfly weed, which has shorter, more numerous and darker green spindly leaves and flowers that are very similar to milkweed. However, it is not the monarch's plant of choice so I keep that in my garden as a backup for when they eat all the milkweed. You can tell if a plant is milkweed by picking a leaf. If it "bleeds" a white milky substance, it's milkweed. If not, it might just be butterfly weed.
And, worst case scenario, if you run out of all those options, a fifth-instar caterpillar will eat cucumber. Buy only organic (from your local farmer's market if you can). Note that they will eat any and all fresh milkweed they can find first and that younger caterpillars will not know they shouldn't eat the cucumber. If they are too young, they will die (I lost a couple last year when I switched them over to cucumber).
I try to be strategic and if I know I have too many caterpillars for the amount of milkweed I have at a time (or that I'll completely decimate a plant mid-summer, giving it no chance to come back in time for fall monarchs), I'll give cucumber to fifth instar caterpillars in early summer. You'll want to get multiple varieties if you can find them. I've had caterpillars choose to eat the stems of a common milkweed plant before fresh cucumber (like the kind you'll find in the store, with thin light-ish green skin) and I've had caterpillars abandon a leaf beginning to dry up only to devour a fresh super-dark green cucumber with thick skin.
Orange aphids can be a huge problem on all milkweed. I try to keep that under control by hosing them down and squishing them between my fingers. Ladybugs will eat aphids (and I think ants will too as I've seen them crowding my plants covered in aphids), but they'll also eat caterpillar eggs. Hence, I've begun picking leaves that have eggs on them and bringing them inside. But, be careful if you decide to do this. If the leaf dries out before the caterpillar hatches, it will not hatch. And, remember, big caterpillars will eat the eggs too so I keep them in the box with only first and second instar caterpillars who mostly stay on their own leaves until they get bigger. I also keep some milkweed in an enclosed mesh laundry hamper. My plan was to allow caterpillars to feast on the milkweed until they got into the fifth instar, then transport them to a box, and that has worked a few times before they run out of milkweed.
There are lots of articles that talk about the lifecycle of the monarch so I won't reiterate that here. It was a surprise to me when I learned about the multiple generations of monarchs and their migration pattern, so you might look into that. I believe that this year I distinctly had four different generations of monarchs. Hopefully the caterpillars that are not yet to fourth instar stage are headed to Mexico when they leave me. Last year was the first time I'd had monarchs from that generation.
Raising monarchs can be a very rewarding experience. My kiddo and his friends at school love watching it too. One of these days I'll get around to building a big monarch "greenhouse" outside with enclosed space for the milkweed to grow and regenerate while caterpillars feast, safe from predators. Won't that be fun!
