Larval Stage (Caterpillar)
Continued: The Monarch Diaries-Rearing Monarchs from Egg to Adult (Part 2)
Adding fresh Milkweed leaves to the container and cleaning up the gooey frass (poop) is a daily task that only takes a few minutes.
As the cats grow larger, shedding their skins, I transfer them to a slightly bigger container with fresh leaves. Clear salad mix receptacles that you buy at the grocery store make great containers at this stage.
Milkweed-Eat & Grow
When the cats reach about 3/4″ inch long, I put them in with the “big boys” in the tomato cage tower that is full of several types of freshly cut Milkweed branches stuck into water bottles. To keep my Milkweed from immediately wilting, I use a flower arrangers trick-flaming the cut ends so that the milky sap stops flowing. I use a small propane torch, like one that you would use for creme brulee. A match doesn’t cut it. It just isn’t hot enough to sear the ends to stop the sap which will make the branch wilt.
All it takes to keep your cats happy and healthy is a good supply of milkweed, because that is all that they eat-nothing else! Eat and grow is the primary goal for the caterpillar. The Monarch butterflies nectar on many types of flowers, but the caterpillars eat only Milkweed. There are lots of kinds of Milkweed, but it must be Asclepias, which is the Latin name for Milkweed. Go to Milkweed Guide to see great pictures and descriptions if in doubt. Growing Milkweed around the country to fuel the Monarchs is really vital to the Monarch survival and people are starting to grow it everywhere. Check out Got Milk…….Weed to read some amazing facts about this essential ingredient to raising Monarchs.
Milkweed is a source of food for many insects, most notably aphids and Milkweed bugs, which I wash off carefully before bringing inside. I don’t want anything else to be eating my collected Milkweed-just my caterpillars!
Instars
Monarchs complete almost all of their growth during the larval stage which lasts from 9 to 14 days, during which time they undergo five larval instars or skin shedding. Before molting, the cat will become very still. If you catch this right after it happens, you can see the skin and then they eat it!
I try not to handle them at all, especially during this vulnerable stage as the larva spins a silk thread to keep attached to the leaf. Â From hatching to pupation, monarchs increase their body mass about 2000 times!
By the time they are ready to pupate the caterpillars become these pudgy clown-like eating machines. So, move them to a large enough enclosure so that they can move to a flat surface, stick, or other hard surface to attach their chrysalis which is their last skin molting or instar. I place sticks in my cage to give the cats added surface area for the chrysalis.
 Making a Caterpillar Tower
As soon as I saw this ingenious enclosure at my workshop by The Monarch Teacher Network, made out of a tomato cage, black tulle, and clothes pins, I was hooked. Taking only a few minutes to slap together and tall enough for Milkweed plants, this was a great solution to keeping the cats contained while being able to observe them. Directions are below.
Directions for Monarch Tower
- Buy a tomato cage with 4 rings. I used one that measured 14″ in diameter and 27″ from the first to the last ring in length. Cut half the length off of each protruding tine and bend the legs at the base inwards.
- Take your 54″ square piece of tulle and knot one end and pull that over top of your tomato cage.
- Laying the cage on the side, clothes pin the tulle to the bottom ring of the cage pulling it taut. Using needle and thread, overcast stitch the tulle firmly to the bottom ring of the cage. Almost there!
Using clothes pins to fasten the bottom of the tulle, use needle and thread to overcast stitch the tulle firmly to the bottom ring 
Overcast stitch the excess tulle to the bottom ring - Using 3 clothes pins, fasten the overlap area of the tulle on the side and place your cage on top of a pizza box base. If you aren’t a pizza lover, cut a piece of cardboard to fit the base.
Use a cardboard base and set your Milkweed into a water bottle - Set up your cage on the base and it is ready to fill with your milkweed plant or cuttings. Tall enough for plants and lots of caterpillars, they will travel to the top when they are ready to pupate. This setup is easy to see through and clean, essential when you have lots of plump cats eating away.
Change out your Milkweed when the caterpillars eat most of it
Disease
I had a few cats die after turning black caused by a bacterial disease. This is upsetting but part of  life. I removed these as soon as I spotted them to stop any spread of infection to others. Be sure to clean and rinse your milkweed before using and clean your cage thoroughly every day to increase your caterpillar survival rates. If you notice a caterpillar looking sick, remove it from the others immediately. Once your caterpillar gets sick, there is really nothing that can be done. You can euthanize by placing in a ziploc into the freezer. For more information on caterpillar diseases, go to 7 Common Monarch Diseases.
I was so excited to see a tagged Monarch hanging out on butterfly weed this weekend. I took a picture but all you can see is that it’s round. Maybe it was my imagination, but with my naked eye it looked like 324. It was breezy thanks to Hermine and it would just fly away if I got too close.
I need to reread everything you’ve written on them. I’m puzzled as to why we just can’t observe them on our milkweed naturally. Are the enclosures just for people who don’t have milkweed nearby?
You can certainly observe them in their natural habitat for any of these phases. But I find it hard to find caterpillars consistently even though I really look hard at all my plants. When I do find a caterpillar on one, then I run in the house to get my camera and when I come back out, it isn’t there! It has moved on that fast. Even with all my milkweed out back, I still have never found a chrysalis and seen a caterpillar form one in the wild. This way, I can be eating breakfast, glance up and see what the caterpillars are doing that moment. Also, the survival rate goes up raising inside, from less than 10% to 90%!
I am so delighted there are people like you in the world willing to do all the work necessary to make these beautiful butterflies happen. I obviously don’t have that kind of patience for it. This was very informative and I certainly hope more are willing to do this good work. Thank you.
Wow, super interesting how you stop the milkweed from wilting. My tropical milkweed finally grew back and I brought in a couple of caterpillars. It wilted IMMEDIATELY. I’m not comfortable with a torch, maybe a lighter? I feel bad, do the caterpillars have any problem with wilted milkweed?