The monarch butterfly, also called the ‘king’ of the butterfly world, is a species with an intricate cycle every year. The monarch butterfly undergoes four generations in a year, and each generation is distinguished into four distinct life stages: egg, larva, pupa, and adult. Monarch butterflies are also the only butterflies that migrate, just like birds do. That is why in this article, we are going to talk about the extraordinary life of monarch butterflies.
Monarch Life Stages & Migration
This journey starts in the oyamel fir forests of northern and central Mexico. Adult monarch butterflies usually emerge from their winter torpor or hibernation, around February or March, when the temperature is just getting warm, and they start looking for a mate. After they mate, they begin flying north and lay their first eggs in March or April. Female monarch butterflies usually lay up to 300 eggs, and they like to put them on the underside of milkweed leaves. These eggs are very tiny; they are just about the size of a pin head.
The eggs of the monarch butterfly typically incubate for about four days until a larva hatches. Larvae are tiny caterpillars, and for the next two weeks, all they have to do is to eat and grow. During this time, they will proliferate and go through a series of molts, where they have to shed their exoskeletons as they outgrow them. The period between each molt is called an instar, and a caterpillar has to go through five instars. The first instar happens right after hatching, and this is when they will eat the leaf they were laid on and their egg casing. During the second instar, the caterpillar grows and begins to turn white, black, and yellow. These colors start to become more vibrant during the third instar, where their tentacles also become longer. During the fourth instar, white dots appear on the prolegs, and at this point, the caterpillar is about one inch long. By the fifth instar, the caterpillar will develop black stripes and start looking for a place to undergo metamorphosis.
The caterpillar will have to find a sturdy spot where they can attach themselves using silk. During this stage, the caterpillar is now called a pupa, or chrysalis, and this is also the stage where the ultimate transformation takes place. At first, the outside of the pupa will be soft, and it will begin to harden in order to protect the organism during its change. It’s also during this stage when they change their color to green to camouflage themselves against predators. This stage lasts for about 10-14 days, wherein the metamorphosis is taking place. What used to be the caterpillar’s mouth will turn into a straw-like tongue, and they will use it to eat nectar from flowers. This is also the stage when they start to grow their wings.
After the metamorphosis is complete, the adult butterfly will emerge. It will take a few hours before their wings are sturdy enough to fly. But when they do, they will immediately head off to feed on nectar and mate. This generation of monarch butterflies will live for 2-6 more weeks and lay eggs before they die. After this, the cycle is repeated, and the second generation of the year will hatch in May/June, the third in July/August, and the fourth hatching in September/October. The second and third generations will repeat the four-stage life cycle, and they will continue to head north as the milkweed blooms; they can even reach the northern USA and southern Canada. But, the fourth generation is different.
This is because the fourth generation will not mate immediately after the adult butterflies emerge from metamorphosis. This is because it is late in the year, and monarch butterflies are not adapted to survive dry and cold weather. That is why they have to migrate back south for the winter months. The other reason why the fourth generation cannot mate yet is that their reproductive organs haven’t matured yet. The fourth-generation will have to go through a phase called reproductive diapause. That is why instead of mating and dying within 2-6 weeks, they will have to migrate south, conserve their energy by soaring on wind currents just like birds that hover in mid-air, then return to northern and central Mexico.
When they arrive back in Mexico, monarch butterflies will gather on oyamel fir trees and once again enter torpor. They will overwinter here and emerge once again when the weather begins to warm up during spring. Then the cycle goes on, and it’s time to mate and start the migration north again, where they will do the process all over again during the following year.
Can you imagine how cool that is? The little monarch butterfly can migrate up to 2000 miles each way, just for them to eat and mate. However, only about 5% of monarchs survive to adulthood, which is why so many eggs are laid. They need water, nectar, milkweed, and oyamel fir forests to survive, and these resources are often in competition with human activities. During different stages of the monarch’s life cycle, their predators may include spiders, ants, beetles, and lacewing larvae.