When checking for eggs, gently turn over each leaf to see the underside. When Monarchs lay their eggs, they land on a leaf and dip their abdomen underneath to lay the egg on the backside. I don’t check every leaf out there - just the ones on the outside that would be the most accessible to the Monarch. Other important leaves to check are the young ones at the top; Monarchs seem to prefer laying their eggs there.
Monarch eggs look like tiny little pearls - very smooth and round. They are generally white but can sometimes be cream-colored. There will be other insects and eggs on the leaves, so you’ll need to focus on spotting the round, white egg sitting alone on the surface. Once you’ve seen one, you’ll identify them more quickly.
I gently cut or snap off the leaf with the egg on it. Try to get the leaf’s stem as well, since this helps it absorb a little water and stay alive. I usually bring a magnifier, scissors, and a container to lay the leaves in. If there are other insects or eggs on the same leaf as the Monarch egg, I run my fingers down it to remove them. You don’t want to bring other critters inside too. There will be a white, milky discharge from where the leaf was cut from the stalk... this is the milkweed sap that Monarch caterpillars thrive on in the leaves. But it can be harmful to humans, so if you're not wearing gloves, be careful not to touch your face or eyes. Once you get inside, wash your hands with soap and water.
I generally find several eggs at a time. If there’s one, odds are there are a few more nearby. I’d like to stress that you don’t have to take them all or find every one. You’re helping the effort just by raising and protecting a number you’re comfortable managing. Remember... these eggs will become hungry caterpillars. Some eggs or caterpillars can be left for nature to do its thing.
So, we’ve found a few eggs... now let’s get them inside. I don’t wash the leaves with eggs on them like I do for the leaves I collect as food - I don’t want to risk harming the egg. Instead, I take a damp paper towel and gently wipe off the leaf around the egg.
Now we need to try to keep that leaf - or leaves - alive while waiting for the eggs to hatch. To keep the leaf fresh, I fold a paper towel several times until it’s small enough to wrap around the stems. Then I wet the folded towel and wrap it around the stems. I follow that with a small piece of tin foil, wrapped around the damp paper towel. I just started doing the tin foil thing this year… and so far, it’s worked well. With just the exposed wet paper towel, it was drying out too quickly and would start to grow mold on the leaf.
What to do if your egg doesn’t hatch before the leaf starts to wilt and die.
That new caterpillar is going to want to be able to eat right away. I get a new, fresh leaf (smaller is better for the young ones), and I take a clean pair of scissors to cut a square around the egg. I then take that postage stamp–sized section of leaf — with the egg still on it — and place it upside down on the new leaf. Now, when the egg hatches, it should easily find the new food source.
Monarch eggs usually hatch within 3–5 days of being laid. It’s a guess, since odds are you don’t know exactly when they were laid—so I just assume five days. If they haven’t hatched after that, then most likely you do not have a Monarch egg… it could be another insect egg or even a small blob of milkweed sap. No worries—just try again.
Watch this fasinating clip of a Monarch Butterfly Egg Hatching
Courtesy Jefferson Lab
I check my eggs at least once a day in their containers to see if there’s any change. When the egg is ready to hatch, your nice, round white egg will turn black. When you see this, you’ll have a very tiny caterpillar the next day. And I do mean tiny! This is where the magnifier can really help. The tiny caterpillar will almost immediately start eating. You’ll see little holes in the leaf if you hold it up to the light. You’ll also notice what looks like flecks of black pepper—that’s the caterpillar’s poop (called frass). You now have a healthy Monarch caterpillar eating!
You should find a location to place the nursery containers near a window for natural light. Not blazing sun… just daylight. The changes in light and temperature are important for their growth and cycles. So, sitting in only artificial lighting—or near a heat or air conditioning vent—is not a good location. Make sure your containers are well ventilated with holes so moisture doesn’t build up inside. Just be sure the holes aren’t so big that a caterpillar could crawl out.
Now is a good time to get out your journal and jot down your notes so far—and grab your Post-its to mark the date each egg was found, along with how many are in each container. I tape those little notes right to the containers. When they become caterpillars, I mark that date as well.
If you spot one egg, there's likely a few more nearby.
Like tiny little pearls - very smooth and round.
Damp paper towel wrapped around stems.
Tin foil around the damp paper towel.
Cutting a square of wilted leaf with egg on it.
Placing square upside down on a fresh leaf.
An egg ready to hatch.
Tiny holes from this caterpillar’s first snack! (a gray background showing through)
Nursery containers near natural light.
Post-its for keeping track.
