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Keeping Monarch caterpillars can be an enjoyable way to study nature. They are easy to catch and readily continue to eat, grow, form their chrysalis, and emerge as a butterfly in captivity.
You will find Monarch eggs and caterpillars on milkweed. The female butterfly lays her eggs on the underside of the leaves, one or two eggs per leaf. She may lay several eggs per plant or may lay only one and fly away looking for more places to lay eggs.
The eggs are very tiny and take a trained eye to locate. The eggs are elliptical in shape and yellow in color. If you locate an egg, carefully remove the leaf it is on from the plant and place in it in a jar with screening secured over the opening. Depending on when the egg was laid, a very tiny caterpillar will emerge in one to three days. At first it will eat the egg casing, but after that you will have to provide it with fresh milkweed leaves.
If you cannot locate an egg, look for the caterpillar. Monarch caterpillars are striped yellow, white, and black. If you locate a caterpillar, carefully remove the leaf it is on from the plant. Place the leaf in a jar with screening secured over the opening. The caterpillar eats for about two to three weeks, growing rapidly during that time. It is important to give it fresh milkweed leaves as needed. Milkweed is the only plant Monarch caterpillars will eat.
As the caterpillar gets larger you will want to place a climbing stick in the jar. Monarch caterpillars always seek a high spot on which to transform into their chrysalis. Most likely the caterpillar will choose the screen over the jar opening to transform into the chrysalis.
The caterpillar will fasten itself to the high spot with a small thread and hang upside down. It’s body will be bent like the shape of the letter “J”. This is a sure sign that it is preparing to transform into the chrysalis. It may hang that way for hours or days, but the final transformation happens remarkably fast. Check often for a chance to see it.
It takes about one to two weeks, depending on temperature, for the butterfly to emerge from the chrysalis. You will know when it is getting close to emerging because the chrysalis will change in color from green to black to transparent.
The new butterfly will need a few hours to prepare its wings for flight. The wings start crumpled and will gradually become flat and more rigid. You may be able to get the butterfly to climb from the jar onto your finger when you’re ready to release it outside. Enjoy the opportunity to observe it closer before it flies away looking for nectar. If it’s not yet ready to fly you can encourage it to crawl onto a leaf or flower in a safe place.
You can also raise Swallowtail caterpillars. Anise Swallowtail butterflies lay their eggs on members of the carrot family. These plants include carrot, Queen Anne’s Lace, dill, fennel, and parsley. Sometimes the caterpillars are even called parsley worms. Anise Swallowtail caterpillars are green with black bands. The black bands have yellow spots. Anise Swallowtail caterpillars are often harder to find than Monarch caterpillars, but you can usually find at least one.
Keep the caterpillar in a jar with screening over the opening. The caterpillar will eat any leaves from the carrot-family plants mentioned above. When ready to form its chrysalis, it will need a stick. Swallowtail caterpillars form their chrysalises on the stick. Depending on what time of year you collect the caterpillar, it will take about two weeks for the butterfly to emerge. If you collect the caterpillar at the end of summer or early fall, it may over-winter and emerge in the spring.
(Photos by Doug Smith, Simply Charlotte Mason)
For more information on raising and identifying many kinds of butterflies, we recommend the wonderful book The Life Cycle of Butterflies by Judy Burris and Wayne Richards.