Monarch butterfly
The monarch butterfly, scientifically known as Danaus plexippus, is a widely recognized species in North America, identifiable by its striking orange, black, and white coloration. Known for their remarkable annual migrations, monarchs navigate vast distances, with the journey spanning multiple generations. Their life cycle includes stages as eggs, caterpillars, and adults, with caterpillars feeding primarily on milkweed, which imparts a toxic quality that deters predators. As vital pollinators, adult monarchs play an essential role in both native ecosystems and human agriculture by transferring pollen while feeding on flower nectar.
Despite their prominence and ecological importance, monarch populations have been in decline, with factors such as habitat destruction, pesticide use, and climate change contributing to their decreasing numbers. Efforts to restore milkweed habitats have had mixed results, and the International Union for Conservation of Nature declared the monarch migration an endangered phenomenon in the 1980s. Despite ongoing research and conservation initiatives, including attempts to secure federal protection, the monarch butterfly was ultimately not listed as endangered in the U.S. as of 2020, although it was classified as endangered by the IUCN in July 2022. The life and migration patterns of monarchs continue to captivate both scientists and nature enthusiasts alike, highlighting the need for ongoing conservation efforts.
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Monarch butterfly
The monarch butterfly is a species common in North America. Monarchs sport a bright orange, white, and black color scheme that makes them easily recognizable. They are also known for their annual mass migrations, which take multiple generations to complete. Their sheer prevalence, striking colors, and migration patterns make them very popular among outdoor sightseers. They are common additions to gardens and other nature-themed attractions.
Monarchs are also essential to both native vegetation and human agriculture due to their status as pollinators. In their adult phase, they drink the nectar of flowers, inadvertently collecting pollen on their bodies when they do so. When they land on another flower to drink more nectar, they deposit the pollen, allowing the plant to reproduce. Since monarchs travel great distances in large numbers, they are one of the most diverse pollinating species of the insect world.
Background
The scientific name of the monarch butterfly is Danaus plexippus. Monarch life cycles are typical of butterflies. They begin as eggs, laid by female monarchs and attached to milkweed plants. The eggs hatch into caterpillars. Monarch caterpillars can be identified by their yellow, black, and white striped patterns.
The caterpillar phase is almost entirely dedicated to eating. It has poor vision and relies on antennae and sensory organs near its mouth for guidance. A monarch's caterpillar phase lasts between one and two weeks, and it grows quickly. At several points during this phase, it will molt. If the shed skin is accessible, the caterpillar will devour it for more energy.
Once a caterpillar has eaten enough, it produces silk to hang from a surface. It then becomes inactive, and it undergoes the changes necessary to become an adult. This phase is known as the pupa or chrysalis, which also lasts between one and two weeks.
Upon reaching maturity, adult monarchs feed solely on the nectar of plants. They mate a few days into their adulthood, and females lay about seven hundred eggs at a time. Adult monarchs may carry out different tasks depending on the time of year they are born. Monarchs that become adults in early autumn begin a long migration. They fly south in massive groups. Most monarchs settle in Mexico or California by the time winter arrives. The temperatures there are warm enough for monarchs to survive, and the generation that reaches these overwintering sites remain inactive until the season passes. At that point, they begin to return north.
The adult phase of summer monarchs is a few weeks, but migratory monarchs can survive for up to nine months. They do this by entering a state called diapause, which delays the development of their reproductive organs and conserves energy. They also spend much of the winter roosting motionless from trees in large groups until spring gets close. At that point, they revive and begin mating shortly afterward. The return journey is a multigenerational affair, with adults finding suitable sites to lay eggs on their way north.
Overview
The milkweed that monarchs eat gives them a toxic quality and unpleasant taste to most natural predators of insects. Their brightly colored wings as adults and stripes as caterpillars function as warnings. Another species of butterfly, known as the viceroy, has a similar appearance to the monarch. Until the late twentieth century, this was believed to be an example of a harmless species mimicking a creature that was more dangerous or undesirable prey, but later findings suggested that the viceroy is just as unpleasant of a meal.
Humans have been able to observe and study monarchs' lifestyle and breeding habits closely, and they are reliably bred in captivity. They are also used in schools to help educate students on butterfly life cycles. In 2009, astronauts brought monarch eggs to the International Space Station. They attempted to raise them to see how they responded to the zero-gravity environment and shared videos of the process with schools on Earth. The monarchs successfully hatched and progressed through their entire life cycle, although their adult phases needed several more minutes to take flight than their Earth counterparts did, and they only survived for a few days after emerging from their pupae.
Monarch migration is a natural phenomenon that has attracted the interest of scientists for decades. It is also a popular spectacle for laypeople, since so many brightly colored insects moving in such large groups is a rare occurrence. Even though scientists had observed the migrations since the early twentieth century, the overwintering sites took decades to pinpoint. Canadian zoologist Fred Urquhart led a study of the monarchs' route beginning in 1937. His team could track the monarchs' course with increasing accuracy over the decades, but it took until 1975 before they discovered the insects' overwintering sites. The studies have led to groundbreaking discoveries about insect communication and navigation.
The monarch population has been in decline since the late twentieth century. This is due to several factors, including pesticides used on crops, the destruction of their natural habitat, and climate change. Humans have also cleared out large amounts of the native milkweed on which monarchs feed. In the early twentieth century, there was a movement to replace destroyed milkweed to help reverse the monarchs' decline. This inadvertently caused more harm to the butterflies. Many planters used tropical milkweed instead of the milkweed native to North America. Tropical milkweed responded differently to the North American climate, which disrupted monarchs' migration cycles.
The International Union for Conservation of Nature (IUCN) labeled the monarch migration as an endangered phenomenon in 1983. By the early twenty-first century, studies showed that the North American monarch population had declined by 80 percent since the mid-twentieth century. In the 2010s, the Center for Biological Diversity and the Center for Food Safety in the United States began a joint effort to obtain federal protection for the monarch butterfly under the Endangered Species Act. In 2016, the United States Fish and Wildlife Service (FWS) agreed to reach a decision on the legal conservation status of monarchs by 2019. In 2020, the FWS found that the monarch butterfly's addition to the endangered species list met the valid criteria, but the agency ultimately declined adding monarchs to the list in favor of other species it deemed more dire. (The FWS also announced that it will continue to monitor and review the monarch butterfly's status.) In July 2022, the IUCN listed the monarch butterfly as an endangered species.
Bibliography
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"Monarch (Danaus Plexippus) (Linnaeus, 1758)." Canadian Biodiversity Information Facility, 9 July 2014, www.cbif.gc.ca/eng/species-bank/butterflies-of-canada/monarch/?id=1370403265690. Accessed 11 Feb. 2017.
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