The Monarch undergoes complete metamorphosis. It starts life as a ridged, spherical egg only l/8th of an inch long. The female produces approximately 300 eggs during her lifetime which are always laid singly on the underside of milkweed leaves during the spring and summer breeding months. She attaches the eggs to the leaves with quick drying glue which is secreted along with the egg. It takes the eggs 4 – 5 days to hatch. A tiny worm like larva emerges and eats the egg shell. Then it eats milkweed leaves almost constantly. On the first day of life it consumes its own weight in food.
The larva (caterpillar) is banded with white, cream, black and yellow stripes. It has three pairs of thoracic legs and five pairs of prolegs which are used to grip. These legs will disappear during the pupal stage. It has 2 pairs of sensory tentacles, one pair on the head and another pair near the end of the abdomen. The caterpillar also has ring-like openings called spiracles that are used for respiration.
The caterpillar molts (loses its old skin) four times as it grows. After each molt it eats its old skin. It stores energy in the form of fat and nutrients to carry it through the non feeding pupa stage. When the caterpillar is about 2 inches long and 3 weeks old, it will stop eating and find a place (like a protected branch) in which to pupate. It uses a special gland in its mouth to weave a small silk button underneath a twig or leaf. It attaches its tail end to the silk button with small hooks in its anal pro legs. Then, it hangs upside down in the shape of a “J”. Soon it begins moving, forcing the skin to split open. It wriggles for up to 5 hours to shed its skin for the 5th and last time.
When the old skin is gone, the new skin hardens into an elegant emerald case decorated with golden dots. This is known as the chrysalis which is the Greek word for golden. During this stage the caterpillar changes into a butterfly as its entire body is reorganized. After about 2 weeks, the butterfly is visible through the transparent chrysalis. The butterfly struggles to split the chrysalis so that it can emerge. This struggle generates the strength needed to fly.
Upon emerging, it hangs from the split chrysalis for several hours (usually in the morning). Its wings are wrinkled and wet and its abdomen distended. The butterfly clings to the casing of the chrysalis while fluids from its abdomen are pumped into the veins of the wings expanding them until they become full and stiff. Some of this orange fluid drips from the wings. After a few hours when the wings are dry and the abdomen reduces to a normal size (usually in the afternoon), the Monarch spreads its wings, quivers them to be sure they are stiff and then flies in a circle and away to feed on a variety of flowers: milk weed, red clover and golden rod.
The Monarch’s diet consists solely of nectar which is about 20% sugar. This food maintains their body and fuels it for flight. They use their vision to find flowers, but once they land on a potential food source, they use taste receptors on their feet to find the nectar and ingest it through a long, flexible, tube-like tongue called a proboscis.
You can easily spot Monarch butterflies at the entrance to Green Cay fluttering through our flowers. They are bright orange with black wing veins and black outer margins. The wings have white spots on outer margins and three orange patches are found near the top of the forewings. The hind wings are very rounded and they are lighter in color than the forewings. The body is black with white spots. The females have broader black vein lines on their wings and the males have scent glands which are marked by a spot of dark scales in the center of the hind wings. The colored markings on the Monarch butterfly signal to their predators that they are poisonous, due to the presence of cardenolide aglycones in their bodies, which the caterpillars ingest as they feed on milkweed. These markings are their protection.
Monarchs live throughout most of the USA, Bermuda, southern Canada, Central America, most of South America, some Mediterranean countries, the Canary Islands, Australia, Hawaii, Indonesia, and many other Pacific Islands. They are found in open habitats including meadows, fields, marshes, and cleared roadsides.
Their life span depends on the season in which the Monarch butterflies emerge from the chrysalis and whether or not it belongs to a migratory group. Adults that emerge in the early summer have the shortest life spans, 2-5 weeks. Those that emerge in late summer survive over the winter months. The migratory adults, who emerge in late summer and then migrate south, live about 8 – 9 months. And those that live all year round in temperate zones like Bermuda, Hawaii, Florida, etc. live 5 – 20 months.
Migratory Monarchs flutter up to 3,000 miles in autumn from breeding grounds in eastern U.S. and Canada to their overwintering habitats in southern California, Mexico, Florida and Cuba. These millions of migrants are going to destinations none of them has ever seen. The generation heading south in the fall represents the great-great grandchildren, or even more distant descendants of the Monarchs that headed north from the above mentioned overwintering habitats the previous spring. Yet the new generations return to the same roosting sites in the south that their ancestors used.
The mating period for the overwintering population occurs in the spring, just prior to their migration north. The courtship is fairly simple and less dependent on chemical pheromones in comparison with other species in its genus. Courtship is composed of two distinct stages, the aerial phase and the ground phase. During the aerial phase, the male pursues, nudges, and eventually takes down the female. Copulation occurs during the ground phase and involves the transfer of a spermatophore from the male to the female. Along with sperm, the spermatophore is thought to provide the female with energy resources that aid her in carrying out reproduction and re-migration.Now the Monarchs are ready to complete their reproductive death run northward to their summer habitat. Females lay eggs daily even though their route covers l, 000 miles. By the end, they have practically no wings left; they’re crawling from plant to plant to lay eggs! It is these succeeding generations that continue the remaining l,500 or more mile journey northward to roosting sites they have never seen.
Studies show that Monarchs orient themselves by using the sun and internal magnetic compasses. This is just a small window of understanding, for what they do is very complex. Insects sense the world in ways we cannot yet conceive or perceive.
From the miracle of metamorphosis to the mystery of migration, the Monarch butterfly remains as a beautiful illustration of the pride, plan, and purpose that abides in the movement of nature.
By Stephanie Canter