Text and Photos: Javier A. Pinzón
Colorful butterflies that fly from flower to flower star in incredible stories. These small insects that flutter about the garden have appeared in myths and legends from time immemorial. They are especially famous for their beauty and unique life cycle, which involves the mystery of metamorphosis. Although this transformation is the characteristic that generates the most scientific curiosity about them, butterflies also have other peculiar traits.
A Complete Transformation
One of the most wonderful aspects of a butterfly’s metamorphosis is that as its body radically changes shape, so does its DNA, the code that makes up the unique genetic imprint of each organism. In butterflies, the unique defining DNA imprint changes as it transforms from a caterpillar to a butterfly. During this process, almost all of the caterpillar’s cells die. The few that survive shut down their caterpillar DNA and turn on their butterfly DNA, and the butterfly then begins to form. Long before the genetic origins of the process of metamorphosis were known —according to the imminent biologist Bernd Heinrich, this process involves the caterpillar’s death and the birth of the butterfly as an independent organism— the Maya, Aztecs, and Greeks associated this transformation with reincarnation, explaining its link to ancient mythology.
Three Types of Plants
To complete this fascinating lifecycle, butterflies need three types of plants. The adult butterfly carefully chooses its host plant, which is where it lays its eggs. The sensory organs of the butterfly’s thin legs allow it to taste a plant’s leaves to determine if it will be good for the young caterpillars when the eggs hatch. Some butterfly species lay their eggs on a single plant species. Once a caterpillar hatches from its cocoon, it feeds off of what is left before moving on to the host plant. Everything is a balance: if caterpillars didn’t have predators, they would end up eating all of their host plants, leaving no food for future generations. Once they become butterflies they require a lot of energy, which they find in plants that have nectar rich flowers. Some species are faithful to the same plant and will spend their short life searching for the right flower to feed on. In between flights, butterflies rest in the shade, bringing us to the third type of plant, which must have large leaves to provide their delicate wings with protection from the sun and rain. Their eyes, made up of six thousand lenses, see ultraviolet light and are designed to find their favorite flowers. The shape of their mouth —a long, thin trunk called a proboscis— has evolved to allow them to reach the pollen within each flower.
Another fascinating thing about butterflies is the delicate variety of colors and shapes we see in their wings. Butterfly wings are actually transparent but we see colors because they are covered with microscopic scales that reflect the light in different shades. Although there are about 165,000 species of butterflies, there aren’t this many different color patterns. In fact, several species of butterflies have the same colors and shapes in their wings, an evolutionary innovation. Some species feed on toxic plants, which make the butterflies themselves toxic, a defense to ward off predators. Over the years, other non-toxic species have evolved to have the same colors and shapes in their wings as the toxic species, thus fooling their predators. Some species have patterns on their wings that resemble large eyes, another trick to confuse enemies. For example, the top side of the morpho butterfly is a rich blue color, but when it poses, its closed wings resemble eight guardian eyes.
The Migration of the Monarch Butterfly
A monarch butterfly has an exceptional life. It embarks on one of the longest migrations known in the animal kingdom, traveling more than eighteen hundred miles from a pair of wooded peaks in northern México to Toronto, Canada. It takes at least three generations to reach this goal, but only one generation is in charge of the return: the “super butterfly,” which flies almost a mile high to take advantage of the wind currents. During their migration, these butterflies search for milkweed, the only plants where they will deposit their eggs, because it is the only food for the caterpillars. This plant is toxic to other animals, making consuming it the monarch’s natural defense. Although a single butterfly can lay about three hundred eggs, one at a time, only 1% of the eggs will become butterflies. In addition to being preyed upon by birds and insects, the loss of milkweed plants along migratory routes and the aerial fumigation of planted fields make survival a difficult task. Accompanied by his wife, the scientist Fred Urquhart devoted his entire life to discovering the origins, travel patterns, and destinations of these butterflies. Although we now know that the sensors of the butterflies’ super antennae tell them the position of the sun and help them orient themselves in space, some of the mechanisms that make this multigenerational migration possible are still a mystery.
The Role of Butterflies
Butterflies require a variety of plants and a balance between caterpillars and their predators, so the numbers and species present in a specific location serve as ecological bio-indicators, telling us about the health and diversity of the environment they inhabit.
Butterflies have several environmental tasks. They pollinate flowers and help in the reproduction of plants. There are also butterflies that feed on decaying fruit, helping the decomposition process. Butterflies provide a food source for many other insects and birds and, by eating their host plants, they serve the role of a gardener, stimulating plant growth by pruning.
Beautiful and Vulnerable
Like many other animals, butterfly communities are threatened by habitat loss. According to a study by Jeremy Thomas from the Zoology Department of Oxford University, the most endangered species are the specialists, the butterflies that are faithful to a particular species of plant. As a consequence, butterfly communities are being dominated by generalist species, i.e., those that use a variety of plant species for metamorphosis and food. So, having a flower garden in your yard is a beautiful way to help butterflies continue brightening our environment, especially if the plants have flowers rich in nectar. As scientists continue to discover the mysteries and wonders of these flying petals, a simple, lovely little milkweed plant by your doorstep will help the monarchs complete their millennial migration.