Watching caterpillar become butterflies is one of the most wonderful, awe-inspiring things you can do with your kids.
If you want to raise monarchs, first, you have to locate a batch of milkweed near you (or cultivate some in your yard.)
Study photos of the plants in books and online so that you can begin to identify milkweed near you.
Over time, I have gotten so good at identifying milkweed that I can see it from several yards away as we fly by on the highway.
And I've been looking for so many years that I know several places where I am likely to find it growing.
But we have some milkweed growing wild near our pond only a few minutes from home, so that's where we usually go to collect the eggs and leaves.
The milkweed patch needs to be close enough to your home (or work or church, etc.) for you to return to it on a regular basis throughout the process of raising caterpillars, because once the eggs hatch, the caterpillars start eating, and will need to keep eating, so you will need a constant supply of fresh milkweed leaves to feed them enough to keep them alive.
Once you find a local source of milkweed, look on the underside of the leaves until you find round eggs like those shown in the picture at bottom.
You can also study pictures of the eggs to be sure you are bringing home the right eggs.
Clip the leaves that have monarch eggs on them off at the stem just using your fingernail, but careful! Milkweed sap is sticky!
It won't hurt you, but it gets everywhere. You'll definitely need to wash your hands once you get home.
Wrap the stems of the leaves in a wet paper and lay them on a plate or platter.
Keep the paper towel moist, adding water to the paper towel as often as necessary. This will keep the leaves fresher, etc.
The eggs will hatch in a few days and the caterpillars will immediately begin eating on the leaves.
Once they hatch, it will be time to go back to the milkweed patch and bring home some more fresh leaves.