The transformation of a caterpillar into a butterfly, known as metamorphosis, is a captivating natural process. Understanding which caterpillars undergo this change helps in their identification and observation.
Telling Butterflies from Moths
To understand which caterpillars become butterflies, it’s important to distinguish them from moths. Both are in the order Lepidoptera but have key differences. Butterflies typically have slender bodies and thin antennae with club-shaped tips. Moths, conversely, often have stouter, fuzzy bodies and feathery or tapering antennae.
Butterflies usually rest with their wings held upright over their backs and are active during the day (diurnal). Moths often rest with wings flat or tent-like and are active at night (nocturnal). Their pupal stages also differ: butterflies form a chrysalis, while moths spin a silken cocoon.
The Caterpillar to Butterfly Journey
The butterfly life cycle involves four distinct stages of complete metamorphosis. It starts with an egg, laid on a specific host plant, which hatches within weeks.
The emerging larva, or caterpillar, focuses on eating and growing. It consumes large amounts of leaves and sheds its skin multiple times (molting) to increase in size. Next, the caterpillar forms a chrysalis, entering the pupa stage.
Inside the chrysalis, the caterpillar’s body transforms into an adult butterfly. This transition can take weeks to months, depending on species and temperature. Finally, the adult butterfly emerges, its wings expanding and hardening before it takes flight and reproduces.
Familiar Butterfly Caterpillars
Several familiar caterpillars transform into butterflies, each with distinct features and host plants.
The Monarch caterpillar (Danaus plexippus) has striking black, yellow, and white bands. It feeds exclusively on milkweed. The adult Monarch butterfly is large, with bright orange wings, black veins, and white spots, typically spanning 8.9 to 10.2 cm.
The Eastern Black Swallowtail caterpillar (Papilio polyxenes), or “parsley worm,” changes from black with a white saddle to green with black bands and yellow spots. It has a retractable orange osmeterium that releases a foul odor when threatened. Its host plants include parsley, dill, fennel, and carrots. The adult butterfly has predominantly black wings with two rows of yellow spots, spanning 6.9 to 8.4 cm.
The Painted Lady caterpillar (Vanessa cardui) is a spiny, grayish-brown or purple-black larva with yellow stripes. It feeds on various plants like thistles, mallow, and sunflowers. The Painted Lady is a widespread species, and its adult form has orange and brown patterned wings with white spots.
Witnessing Metamorphosis
You can responsibly observe a caterpillar’s metamorphosis. Start by finding caterpillars on their host plants in nature. Create a ventilated enclosure, such as a container with a mesh lid, for observation.
Provide fresh host plant leaves daily; caterpillars get all their hydration from food, so open water is unnecessary and a drowning risk. As the caterpillar prepares to pupate, add sticks or vertical surfaces for chrysalis formation. After the butterfly emerges, allow its wings to dry and harden before releasing it into its natural environment, ideally near nectar sources.