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If you came from the first article, then you should have your Butterfly eggs in some sort of container. It can be a to-go food container, or it can be a condiment cup you aren't using.

In a few days to a week, your egg(s) will hatch. The amount of time it takes for the caterpillar to hatch depends on the temperature and the amount of sunlight. If temperatures are below 45F here in PA, they will die. Butterfly eggs should be kept out of direct sunlight and kept in a room with constant temperatures of 60-80F (this can be your patio.)

Once the caterpillars hatch, they look nothing like their 5th-instar selves. They look like little grubs. Newborn caterpillars can range from 0.5mm to 3mm in length. This is called the "first instar." First instar caterpillars will not eat that much, their leaf-munching barely visible. This is when you should take caterpillars in. First instar caterpillars have a very unlikely chance to be parasitized, so you don't have to worry about maggots coming out of your baby caterpillars.

Caterpillars molt like a snake. They shed their skin 5-6 times, and they do this when they get too big for their skin (they do not have bones). The next molt is called the "second instar". Usually, this is when the caterpillar will get the colors and markings it will have as a fully-grown caterpillar. At this stage, they can do noticeable damage to your plants, and are more susceptible to being parasitized.


If you have access to the host plants of the caterpillar you are raising, then at this stage you should snap off 1 leaf (size depends on how many caterpillars you have). They should eat enough that they need to molt into the "third instar".

Third instar caterpillars look like bigger versions of their second instar selves. The only difference? They poop EVERYWHERE!

Caterpillar poop (called "frass") is the caterpillar's waste after a good snack. A cool thing about caterpillars is that they can poop while they are eating! It's really weird but really cool.

When your caterpillars are in the third instar, their poop is going to be everywhere in your container. A simple way to deal with this is to clean your container once every 1-3 days (preferably when you put new leaves in). A good way to do this is to soak the container in water until it is filled with water. Then, dunk the water back into your sink. Do this 3 times, then wipe it thoroughly with a paper towel. Add the new leaves and caterpillars back in, and then you'll be fine! (Until they make a mess again).

The next molt is called the "fourth instar". Again, the caterpillars just look like bigger versions of their third instar selves. But now, they can completely defoliate your plant in a few days. They will eat and poop a LOT, so be ready. Follow the same steps as you did with the third instars, and you should be fine. Make sure to give them extra leaves, especially if you are going on a trip.

The final molt is called the "fifth instar". They will be as big as they will get in this stage, and they will finish off huge leaves in a few hours. If you are going on a trip, you should bring your fifth and fourth instars with you. A few days after molting, though, a big change will occur...

A Monarch egg about to hatch.

A Newborn Monarch caterpillar.

A second instar Black Swallowtail caterpillar.

A third instar Monarch caterpillar below its frass.

Third and fourth instar Pipevine Swallowtail caterpillars.

A fourth instar Zebra Longwing caterpillar.

A fifth instar Gulf Fritillary caterpillar.

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