Black Swallowtail butterflies glide around my garden in the summer. I have a little caterpillar nursery in my greenhouse. Swallowtail caterpillars are sometimes called parsley caterpillars. They seem to like to eat my dill plants. I don't use any pesticides, so I always have a good amount of swallowtail butterfly caterpillars and chrysalis cases to observe. The brightly colored caterpillar warns birds that it may be poisonous. It's a great defense.
Children are wonderful at observing nature and finding caterpillars very quickly. Just use your favorite search engine to find caterpillars and butterflies that are in your area. Look for host plants that caterpillars eat. For example, where I live Monarch caterpillars eat milkweed plants, Eastern Swallowtail caterpillars eat parsley, dill and fennel plants. The eggs are usually the size of white rice.
Make a butterfly garden . Flower boxes make great butterfly gardens too. The more variety you provide in your garden, the more butterflies and bees it will attract.
Here are two books about butterflies that you might want to consider checking out from your local library.