Here are some basics. I’ll add photos and more information soon. There almost as many good ways of raising monarchs at home as there are people doing it! So improvise.
The basics are:
- The container needs to be tall enough that a butterfly can emerge from its chrysalis and hang with its wings fully extended to dry and harden.
- You must always provide fresh milkweed for caterpillars.
- You have to control moisture.
Early instar caterpillars can drown in a drop of water and too much moisture can support both fungus and bacterial growth that can be bad for the caterpillars. If it is too dry the milkweed dries out quickly and the caterpillars don’t get enough water in their diet. - You have to keep the enclosure clean.
Frass must be cleaned out regularly. It also is a source for mold and bacterial growth. As the caterpillars get bigger there will be more and more frass. - Your container must keep out predators and parasites.
Fine mesh is necessary to keep out the tiny wasps (At first glance they look like fruit flies or gnats) that can parasitize caterpillars as they transform into chrysalides. Tachinid flies that look just like houseflies lay eggs on caterpillars. When the maggots hatch they burrow into the caterpillar and eat it from the inside out.
This is what I do:
Lots of different containers work. For eggs I like small plastic storage containers, because it is easier to see what’s going on and control humidity, which is a lot of what you have to accomplish. I raise a lot of caterpillars most summers and am partial to plastic shoe boxes for the older guys. If you want to display your caterpillars, aquariums, jars, bug/hamster boxes, and all sorts of other things work.
I collect eggs because it is easy to protect the caterpillars from parasites if you have control of them from the time they hatch. Parasites emerging from older caterpillars can infect the rest of the stock with which they share a container.
Common milkweed (Asclepias syriaca) is the dominant milkweed on the east coast into the Midwest. Those leaves are usually large enough that you can just pluck the leaf that the egg is on. I put them in a closed container with bounty paper towel on the bottom and check them regularly.
The egg will hatch within 4 days of when it was laid in weather averaging 75°, faster if it is warmer. If the leaf dries out before the egg hatches, snip the part with the egg off of the old leaf with a pair of scissors and place it on a new fresh leaf. (1/4″ square is big enough and won’t tend to dry out and wrap around the egg. Sometimes newly hatched guys get confused and sit in an old dried up leaf when there is good milkweed all around them.)
Make sure you regularly give your little caterpillar fresh leaves.
Once caterpillars make it to 3rd instar (and that is somewhat arbitrary, based on what I can spot and take care of easily) I move them to a larger container.
It is easier to keep leaves fresh in a larger container. Cut stems of milkweed about 4 -6 leaves long (or whatever fits your container) and wrap the bottom in a paper towel. Dip the paper towel and stem in water and collect as much as it will hold then stick it in a baggie, wrap the excess baggie tightly around the stem and secure it with a rubber band–I like the folded sandwich baggies they are easy to work with. I’ve also used twist ties, but rubberbands hold on better. I’ve also used florist tubes for water but they tend to go dry too fast for my liking. The paper towel and baggie method was what I started with and after a couple of years of using the supposedly “new and improved” florist tube method I went back.
From that point on I just keep replacing the milkweed and cleaning out the frass once or twice a day. It is best if the top of the container is a good place for the caterpillar to go into j and make its chrysalis because most of them will go to the top for that.
The Moisture Problem.
If you use a container cover that air flows through (I really like to use cut up stockings for lids–the top part of panty hose with the legs knotted and cut off for bigger containers) and you have air conditioning the leaves could dry out. In that case I keep the paper towel on the bottom of the container slightly damp. If you have a solid lid container that no air goes through moisture could collect…in that case I use a dry bounty [a[er towel on the bottom and keep an eye on the container and wipe it dry, when necessary— at least once a day.
My favorite covering for plastic containers is panty hose…seems to keep the moisture level perfect. I use the legs, cut in sections and knotted for small containers and for bigger containers I use the seat with both legs cut off and knotted. The elastic in the hose holds the material in place and if you use sheer it’s easy to check out if anyone is in “j” on the inside before you remove the lid. It just isn’t quite as “pretty” for show…but it is the rule of the day at my house.
If you don’t use pantyhose and are just buying them for lids, the cheapest brands are the best. When I am doing classes and have a lot of pint size containers for different instar caterpillars, I buy a box of cheap knee highs. I like the black ones best. They are easier to see through for some reason.
For a show use an aquarium or bug box. You can also use a plastic container, cut out an area on the plastic lid and hot glue screening material over the hole.
If you are having trouble with disease or you want to be particularly careful, putting just one caterpillar in a container creates a firewall and protects the caterpillars from infecting each other.
If the caterpillars all seem pretty healthy, I will put 4 in a medium sized container (like a bug box) and up to ten in a larger container. It is important that all of the caterpillars in the container are about the same instar (size) and make sure there is always plenty of food…so they don’t munch on each other. You have to keep it clean which becomes more of an issue as they get bigger. They eat more and the frass gets bigger too!
You need to be able to sterilize your containers. Clean with a mild bleach solution and rinse well.
Don’t allow butterflies to eclose in the same container with younger caterpillars. A major monarch parasite is a protozoan parasite which can only live in the caterpillar stage of the monarch. When the caterpillars become chrysalides the protozoan become spores which migrate to the areas that will become scales on the butterflies. A newly emerged butterfly that was infected by the Oe protozoan can drop spores onto the milkweed that caterpillars are eating. If the caterpillars ingest the spores they will be infected. If they ingest a lot of spores the infestation can kill them.
Monarchchaser's Blog 
let’s just call you the monarch mothering expert…lol! way to go.
Thanks for all this great information.
Great info.
I have been raising monarchs for years
Never knew about the protozoan parasite.
Any ideas, why some caterpillars do not manage to form into a chrysalis and die hanging upside down?
I raised monarchs for years before encountering the protozoan parasite,Oe, too. I first became aware of it when I set up breeding tent. One infected adult can wipe out a whole generation of caterpillars in an enclosed situation like that. It can be devastating. Oe can kill a caterpillar as it is trying to go into chrysalis and after it has become a chrysalis too. Tachinid fly maggots, bacterial infection, fungus infection and dehydration can do it too. In my area it is not unusual for 50% of caterpillars in the wild to be parasitized by tachinid flies. Watch for maggots or little brown pupae in the bottom of the container where the caterpillar is hanging trying to become a chrysalis, also the tachinid fly maggots will often leave behind a string hanging from the dead caterpillar or chrysalis.
Better to use vinegar rather than bleach. Bleach leaves a residue that is almost impossible to totally rinse off and you cannot see it!
I agree with you about vinegar rather than bleach for everything but monarch rearing container decontamination. Vinegar will not kill the Oe spores which are one of the main reasons that cleaning the containers is so important. I do not generally use the bleach rinse during the season while I am raising the caterpillars. I do a major cleaning with bleach at the end of each season. During the season, I am careful not to put caterpillars in containers in which adults butterflies have eclosed (emerged). The spores drop from the bodies of infected adults and caterpllars become infected when they ingest them. The protozoan does not become a spore until the caterpillar becomes a chrysalis–so the protozoan is not passed from caterpillar to caterpillar, only from adult to caterpillar. The bleach residue is a problem, perhaps rinsing with vinegar afterward would help.