We see loads and loads of butterflies this time of year. They're doing the last minute egg laying thing and it's pretty common to find little caterpillars in the garden.
If you're interested in hatching your own butterflies, then look for caterpillars on the parsley, fennel and dill plants in the garden. That's where the swallowtail caterpillars hang out. If you're near fields, then check milkweed, too, for monarch caterpillars. Look for chewing damage, holes in leaves and frass [poop]. The larger the caterpillar, the faster you'll see a butterfly.
Check this post for how we raised swallowtail caterpillars. This post is about how they turned into chrysalises. This post is about how we stabilized the chrysalises. And this post is about how they emerged into butterflies.