by Linda Martinson
Recently, I was walking with a seven-year-old friend while she collected caterpillars. She placed them on her arms and on the handlebar of her scooter and wondered how many legs they had. I mentioned to her that, hopefully, all of her caterpillars will turn into butterflies. She glanced at me skeptically and said, “I just can’t understand how that happens.”
The large insect order of Lepidoptera comprises both butterflies and moths, insects with four wings covered with minute, overlapping and often colorful scales. There are many more moths than butterflies in the order, about 89-94 percent moths to 6-11 percent butterflies, and their distinguishing characteristics are sometimes confusing. Although both butterflies and moths are caterpillars in their larval stage of life, and many of them could be described as fuzzy, there are no fuzzy butterfly caterpillars, only smooth. So we could be confident that my young friend’s caterpillars, all smooth, would become butterflies if not eaten, stepped on, or over-collected.
It is indeed a challenge to understand the amazing metamorphosis from egg to larval stage (caterpillar) and then to the pupal stage (called a chrysalis for butterflies and a cocoon for moths) finally to adult butterfly or moth. And the metamorphosis of Monarch butterflies is especially complicated: they go through four stages during one life cycle and through four generations in one year.
Monarch butterflies are colorful with distinctive wing patterns; they are generally considered the most beautiful and majestic of butterflies. They also have some fascinating characteristics that are different from those of other species of butterflies. For example, they flap their wings at about a quarter of the speed of other butterflies. Monarchs fly slower and more majestically than other butterflies because they are poisonous to their predators such as birds, frogs and lizards. In their caterpillar larval stage, Monarchs eat and store a poison from their exclusive diet of milkweed leaves that makes them toxic to predators throughout their lifetime. Their striking color and markings advertise only beauty to us, but clearly broadcast “poisonous-do-not-eat” to potential Monarch butterfly predators.
Female monarchs have thick bold veins and males have two small patches on their wings.
The strange and mysterious characteristic of the life cycle of Monarch butterflies is that there are four unique annual stages in the life cycle of Monarchs that are completed by each of four successive generations of each butterfly,. During the complete cycle, three separate Monarch butterfly generations go through the four life cycle stages as described above, but the fourth Monarch generation goes through a cycle that includes migrating to Mexico, hibernating and returning north to begin again this generational cycle again.
During Stage 1, early in the year, after wintering in Mexico, Monarch butterflies locate a mate and then migrate north to search for just the right milkweed plant upon which to lay their eggs. After about four days, the eggs hatch into caterpillars and they begin eating milkweed leaves.…vigorously! A caterpillar can eat a complete milkweed leaf in just a few minutes, and they will gain about 2700 times their original weight in their short life span of about two weeks. Then each caterpillar will attach itself to a leaf or stem and begin the process of metamorphosis by transforming itself into a chrysalis. During the 10 days of the chrysalis phase, the caterpillar is going through an amazing change into an adult butterfly. After emerging from a chrysalis, the mature Monarch butterfly then flies around, feeding on the nectar of flowers, and finding a mate during its short but relatively carefree life of about two to six weeks.
During the next two to three months of the year, Stage 2, the new first generation of Monarch butterflies lay their eggs and then die. Then the eggs begin the larval stage, the hatched caterpillars eat, grow and undergo metamorphosis into a chrysalis and then hatch into the second generation mature butterfly. It then lives out its short but colorful and free lifespan flitting around feeding on flowers and laying eggs.
During the summer months of the year, Stage 3 occurs: a third generation of Monarch butterflies lives through the same life-cycle as the first and second generations, i.e., mate, lay eggs which hatch into caterpillars that and eat voraciously, grow, transform into the chrysalis stage, and then hatch into butterflies that fly around, sip nectar, find mates.
The fourth generation repeats the same life cycle of mating, laying eggs that hatch into caterpillars that eat voraciously and grow vigorously, then changing into chrysalises that hatch into a mature butterflies, with one additional and astonishing step, Stage 4.
The fourth and final generation of Monarch butterflies in a year also migrates in the late summer hundreds of miles back to Central Mexico where they will roost hanging from trees all winter, living for six to eight months (instead of just a few weeks, and then they migrate back to the United States in the early spring — certainly a fascinating life cycle.
Monarch butterflies are vulnerable during their migration and at their winter sites in Central Mexico where millions of Monarchs roost for the winter in huge groups in the trees. Their intricate and precarious migration pattern has been given a “threatened phenomenon” status by the International Union for Conservation of Nature (IUCN). In 1986, the Mexican government established 62 square miles of forests as a Monarch Butterfly Biosphere Reserve, and this area was further extended to 217 acres in 2000. But there is still a lot of pressure in Mexico to limit their winter habitat and they are, of course, also vulnerable migrating back north.
Monarchs in the United States have lost an estimated 165 million acres of breeding habitat due to development and herbicide spraying. Milkweed plants have been almost eradicated in several areas largely due to increased herbicide spraying, mostly on corn and soybean crops that have been genetically modified to tolerate direct herbicide spraying.
There are several areas and communities, especially in the eastern United States, in Western North Carolina, and locally at Richland Ridge, that have planted milkweed for the caterpillars and where several varieties of flowers and several native wildflowers as nectar sources for the mature butterflies including Monarchs. For example, at Richland Ridge there is a 150 yard stretch of beaver ponds, marshes and meadow with several wildflowers attractive to butterflies including Joe Pye weed, ironweed, asters, coreopsis, jewel weed, asters, Turk’s Cap lilies and Queen Anne’s lace. Butterfly weed and Swamp milkweed have also been planted and several Monarchs have been spotted every year from early spring and especially in the fall, so eventually we may be able to establish a multi-acre Monarch Way Station along the West Fork of the French Broad River.