One of the world’s most easily recognizable butterfly species –the monarch butterfly or simply monarch is an iconic pollinator belonging to the Nymphalidae family and Danainae subfamily. Well known for its large wingspan, orange hues, and fascinating patterns, the monarch is a well-researched and well-documented butterfly breed that continues to stir curiosities within the Entomological community. The scientific name used for the monarch butterfly is Danaus Plexippus, and of its, some other region-specific names include – milkweed, common tiger, wanderer, etc. The distinguishing features of the monarch are its large orange wings with a wingspan of 9.2 to 10.2 centimetres, which are laced with black lines and bordered with white dots. The monarch butterfly is indigenous to warm areas where milkweed can grow. Thus, they are concentrated in North, Central, and South America with scattered presence in Australia, India, and Hawaii. Unfortunately, the monarch butterfly has ceased to exist in South America in recent times. It is a widespread belief that the butterfly was named ‘monarch’ as a homage to King William III of England.
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Migration and Monarch Butterfly
The long, seasonal migration of the monarch butterfly distinguishes the species from its peers. It is the only butterfly known to make a two-way migration similar to birds. The monarch butterfly migration is the longest within the insect kingdom as they undertake a tedious migratory journey of 4634 kilometres. The monarch butterfly migration is a spectacle mainly confined to North America. The monarch butterfly species migrate every summer and autumn to and from areas on the Western coast of California or on the mountainous regions in Central Mexico.
The eastern North American monarch variety is notable for its annual southward migration during the late summer or autumn season. Around 500,000 monarch butterflies migrate from North and Central America and Southern Canada towards Florida and Mexico. As days get shorter and the temperature gets colder, the monarchs realize that it is time for them to abandon their breeding grounds in the Northern USA and Canada and fly south to the warmer mountains of central Mexico. After the days get longer and warmer again, they transcend thousands of miles and endeavour a multi-generational return to the north. The monarch butterflies stop somewhere on their northward return journey to lay eggs, and the new generation again continues farther north and stops to lay eggs. This process may repeat over four to five generations before the monarchs can finally reach Canada again. On the contrary, the western North American variant of the monarch butterfly migrates to sites in Southern California, but they have also been observed in overwintering Mexican regions. The overwintering forests of the monarch are protected within the Monarch Butterfly Biosphere Reserve, a UNESCO World Heritage Site.
But, the pressing question is how do monarch butterflies make such long and dangerous expeditions? Studies have revealed that they utilize the sun to stay on course, and they also possess a magnetic compass that allows them to manoeuvre on cloudy days. Acquainted with a unique gene, the monarch butterfly species are accustomed to long-distance flights.
It is vital to mention that not all monarch populations undergo long migrations. For example, some monarchs in Australia and New Zealand migrate much shorter distances. Furthermore, some populations of the butterfly in North and Central America do not migrate at all.
The massive monarch butterfly migration has been deemed ‘one of the most spectacular natural phenomena globally.’
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The Life Cycle of the Monarch Butterfly
We have already answered the questions – what is a monarch butterfly, and what its migratory patterns are. Let us now move forward to the topic of the life cycle of this fascinating species.
The monarch butterfly life cycle undergoes four stages of complete metamorphosis. The female monarch butterfly lays all her eggs individually on a milkweed plant’s leaf. She attaches the leaves with a glue-like paste secreted from her proboscis. A female monarch generally lays 300 to 500 eggs over two to five weeks. After a few days, the eggs burst into small larvae or caterpillars. The primary purpose of the monarch caterpillar is to grow. Thus, they spend most of their time eating. They indulge in milkweed for about two weeks and, after that, spin a protective case around themselves. With this spin, the caterpillar officially enters the pupa stage. Alternately known as a chrysalis, the pupa stage extends for a week or two, after which the metamorphosis is complete and a fully formed, black and orange-tinted adult monarch butterfly emerges.
Let us try and further scrutinize each stage of the monarch butterfly life cycle.
Eggs – The eggs of the monarch butterfly are either cream-coloured or light green with an ovate to a conical shape. Approximately 1.2 × 0.9 mm in size, the eggs of the monarch butterfly weigh less than 0.5 milligrams. Females lay eggs on the downside of the milkweed leaves as the monarch caterpillar only consumes milkweed leaves. This small tactic allows the young ones to feed efficiently and stay away from predators.
The Caterpillar – The caterpillar goes through five major distinct stages of growth. The caterpillar grows larger in each stage because of eating and energy storage. The caterpillar, also known as instar, lasts for about three to five days, depending upon different factors like temperature and food availability. The first caterpillar that erupts out of the egg is pale and translucent. During the second stage, the instar develops a characteristic white, yellow, and black transverse bands pattern. Furthermore, pairs of black tentacles also begin to grow. The third monarch caterpillar has longer tentacles and more distinct bands. During the fourth and the fifth stage, the instar larva develops more complex banding patterns and white dots on the prolegs. During the final stage, the caterpillar has a voracious appetite and can consume a large milkweed leaf in one day. After completing its growth, the caterpillar is 4.5 to 5 cm long and 7 to 8 mm wide, with a body weight of 1.5 grams.
Pupa – To prepare for the pupa or chrysalis stage, the caterpillar selects a safe space for pupation where it spins silk covering on a downward-facing horizontal surface. During the pupal stage, the adult butterfly forms inside the protective cocoon. It is fascinating to see that the exoskeleton first becomes translucent within a day or two before emerging, and the chrysalis turns bluer. Consequently, within twelve hours, the exoskeleton becomes transparent, revealing the orange and black hues of the butterfly inside before the emergence.
Adult – An adult monarch butterfly is born after two weeks of the pupal stage. The adult butterfly first erupts out as a chrysalis and hangs upside down for a few hours until its wings are dry. Monarch butterflies engage in different things depending on the time they complete their metamorphosis. If they emerge in the spring season or early summer, they begin reproducing within days. On the flip side, if they are born in the late summer or fall, they know that winter is ascending, and it is their time to head south for the warmer weather. During the breeding season, spring and early summer, the adults reach sexual maturity in four to five days. However, the migrating generation does not reach sexual maturity until overwintering is complete.
The monarch butterfly's metamorphosis from the egg to its flighty form occurs within 25 days during the summer and takes about 49 days during cooler conditions. During the development process, the larvae and the milkweed hosts are susceptible to weather exigencies, predators, parasites and diseases. Statistics reveal that less than 10 percent of monarch eggs and caterpillars survive in the egg. But, this is a natural attrition rate for most butterflies as they are lower on the food chain.
Interesting Facts About the Monarch Butterfly
Being one of the best document butterfly species, the monarch butterfly or Danaus Plexippus is encapsulated with quirks and wondrous phenomena. Therefore, we have catalogued a list of some fascinating monarch information.
The shape and colour of the monarch butterfly wings change as they appear redder and elongated at the beginning of the migration.
The wings shape and size differ for migratory and non-migratory monarch butterflies. Monarch butterflies from eastern North America possess larger and more angular forewings than their western counterparts.
The flight of the monarch butterfly has been designated as ‘slow and sailing; It has a flight speed of 9 kilometres per hour. For comparison, an average human jogs at a rate of 9.7 to 12.9 kilometres per hour. As such, the flight of a monarch butterfly is so smooth and speedy that it is akin to a human being jogging in full spirit.
Like all adult insects, the monarch butterfly has six legs and only uses its middle legs and hind legs for walking as the forelegs are small and held against the body.
The bright orange colour of monarch butterfly wings is primarily used to warn predators of their bad taste. The eye-catching colours of the butterfly warn predators that they are poisonous and taste terrible. The poison of the monarch butterfly comes from toxic milkweed leaves. But, monarchs have evolved to tolerate the poison and use it for their benefit by storing the toxins in their bodies and turning themselves poisonous to predators like birds.
Another exciting piece of monarch information is that they have been bred on international space stations.
Intriguing, feisty and wondrous, the monarch butterfly is a natural marvel whose life cycle, patterns and behaviours open a Pandora’s Box of evolutionary intelligence. These beautiful yet bold butterfly species have fascinated the scientific community with their traits and have tickled the laymen through their beauty. Despite unprecedented strides in documentation and research, there is a lot to know and garner about monarch butterflies.
On account of excessive human infiltration and interception, the monarch butterfly population has declined dramatically. In addition, the disappearance of milkweed leaves has been a significant reason for the reduction in the monarch population. Studies show that the eastern variant of monarchs has declined by 80 per cent; whereas, the western variant has fallen by a whopping 99 per cent since the 1980s. The hour’s need is to protect, safeguard and conserve this beautiful butterfly species through collective means. Governmental and non-governmental impetus is necessary to protect monarchs from further disappearance.