One of the most amazing feats of nature is the metamorphosis of a caterpillar into a butterfly. Because butterflies and moths are so prevalent in North America, there is ample opportunity to observe this form of metamorphosis in all its phases.
All butterflies begin their lives as an egg. Butterflies are quite particular about where they lay their eggs, taking care to place them on plants that the caterpillar will eat. Many butterflies will also lay only one egg on one leaf, as a protection from predators and cannibalistic newborn caterpillars. When the egg hatches, a tiny caterpillar emerges, known as the first instar phase. Its very first meal will be the egg casing from which it came, after which it will move on to the young, tender leaves of the host plant.
Caterpillars are constantly consuming food, which makes molting a recurring part of life. After the first time it sheds its skin, it moves into the second instar phase, with a slightly looser skin to fill out. Two more instar phases follow, during which the appearance of the caterpillar will begin to change. In the fifth and final instar phase, the new skin beneath the last layer shed forms the outer shell of the chrysalis, or pupa.
It is at this point that metamorphosis begins to take place. The wings of the butterfly have been forming beneath the caterpillar’s skin since before the final molt, and continue to develop in the safety of the chrysalis. The chewing mouth parts of the caterpillar are transformed into the sucking mouth parts of a butterfly, and antennae begin to form. Within 10-15 days of forming the chrysalis, a butterfly will finally begin to emerge, where it will pick up where its predecessor left off to continue the species’ legacy.
The zebra swallowtail enjoys a total life span of about 2 months from egg to butterfly, depending on factors like environment and temperature. The juvenile caterpillars start out completely black, but as they mature, they begin to change to a greenish color with yellow, black, and white stripes. Once the zebra swallowtail becomes a butterfly, its main focus will be on reproduction. This species prefers the trunks or leaves of the pawpaw tree.
Monarchs also typically have a life span of 2 months, but this is variable based on the season and the generation a monarch is born into. Butterflies produce between 2-4 broods annually, and the fourth brood of a monarch species will migrate south for the winter, outliving its predecessors by as many as 6 months. The monarch lays its eggs and feeds on milkweed plants.
The Red Admiral is unique in terms of life span because it has the ability to hibernate during winter months. It is a highly migratory species, primarily found in warmer climes, moving north to breed in the spring. The caterpillar of the Red Admiral is black and thorny, while the butterfly has dark colored wings with orange and white accents. These insects are partial to nettle plants.
The cloudless sulphur is another migratory species, and its life span depends wholly on what region it lives in. Tropical species will breed continuously, while migratory species may only produce 1-2 broods per year. The cloudless sulphur caterpillar will take on the coloration of whatever it is feeding on, resulting in various shades of yellow and green, sometimes almost bluish. The same applies to the coloration of their chrysalis. These butterflies lay their eggs on the leaves of senna and woody pea plants.
The painted lady is the most widespread butterfly in the world, found in every region except South America, Australia, and Antarctica. Their life spans are typically short, often extending no more than a few weeks from egg to butterfly, depending on the climate. Interestingly, the wings of the painted lady butterfly are outfitted with solar cells, which harness the sun’s heat for energy. Painted lady butterflies are partial to thistle plants for laying their eggs.