Monarch Rescuer Tells Intriguing Tales

The St. Thomas Field Naturalist Club celebrated its 60th anniversary at an annual banquet dedicated, in part, to the monarch butterfly.

Guest speaker Laura Hathaway, a certified monarch rescuer, is passionate about Danaus plexippus.

Hathaway shared stories of her hobby and gave numerous intriguing facts about the “milkweed butterfly” whose catapillar lives on milkweed and is named the monarch because of the golden ring crowning its chrysalis.

Hathaway rescues eggs or caterpillars (larva), along with the milkweed from farm fields and headlands about to be sprayed or from lands about to undergo development.

She brought along some of the tools of her hobby: a plastic soda bottle nursery; a hanging frame for the pupa (crysallis) and a net tent for the emerging butterfly.

Anyone can be a rescuer but must have certification from the Ministry of Natural Resources.

Monarchs are the only North American butterfly to migrate 4,000 kilometres southwest to hibernate in their wintering grounds on patches of firs high in the Sierra Madre Mountains of Mexico. Butterflies that emerge late in summer and early fall fly south without ever having been there before.

A monarch from St. Thomas will not be back here the following year. It will be its great-grandchild. On the return journey, the butterfly follows the sun and milkweed north, reproduces and dies. Yet somehow the next generations know and follow the same route their ancestors took, sometimes even returning to the same tree.

Scientists are aflutter over the butterfly’s future. Natural disasters, reduced acreage of milkweed in its summer home and habitat loss in Mexico all threaten its survival .

The monarch undergoes four stages of development. The egg hangs onto the underside of a milkweed leaf and with luck will hatch. A female butterfly deposits as many as 700 eggs but only seven will make it to adulthood in the wild. Hathaway’s rescue averages an 8% success rate.

If conditions are right, the egg hatches into a caterpillar. At birth, the caterpillar is the size of an eye lash, but in two weeks, gorging on thousands of milkweed leaves, shedding its skin four times, it weighs 3,000 times its birth weight.

By eating milkweed, the caterpillar protects the future butterfly from predators. Milkweed contains a toxin that is distasteful and harmful to predators. Birds associate the monarch’s bright orange colour with an awful taste and avoid it.

The orange viceroy butterfly rides on the coat tails of the monarch. Because of its similar colouration, it too is avoided by birds.

Hathaway waits for her rescued caterpillar to assume a “J” shape, indicating its readiness to form the beautiful shimmering chrysalis.

Once in this stage, Hathaway suspends the chrysalis on a hook in the net tent where it will be safe to complete the life cycle.

Inside the chrysalis the caterpillar’s structure dissolves and the metamorphosis into an adult butterfly occurs. Within several weeks, the chrysalis skin splits and a monarch emerges. It pumps fluids into its wings then waits for the fluid to harden before it takes flight.

Male monarchs have black coloured scent glands on each hind wing.

Hathaway releases the adult butterflies into the wild.

Researchers at the University of Kansas proved the monarch has its own internal compass and can detect the magnetic field of the earth. This was tested in the laboratory on groups of monarchs under three different magnetic situations:

With no magnetic field, butterflies flew in random direction. With a reverse magnetic field, butterflies flew northeast. With a normal magnetic field, the butterflies flew southwest as if migrating.

However, the monarch is not without mystery. How do they know that southwest is the right way to go? And what prompts them to migrate?

In the laboratory, in their cages, the butterflies became restless and flew about when some instinctive urge prompted them to migrate.

Recent research at the University of Guelph found that great numbers of monarchs from this area also migrate over the Appalachians and settle on the eastern seaboard where milkweed abounds later in the season. They eventually proceed southwest and meet up with their counterparts in Mexico, but much later than those who took the direct route.

A biologist at Emory University in Atlanta found that monarchs are their own doctors and medicate their potential offspring. Susceptible as caterpillars to parasitic invasion of the gut, the female butterfly can pass the parasite into its eggs.

Healthy females lay their eggs randomly on any milkweed handy. The parasite-infected female lays her eggs on the most toxic species, utilizing a group of chemicals called cardenolides.

This is exciting for humans as the monarch gives clues as to what plant chemicals may be useful for human medication.

Hathaway also tags butterflies in the fall. This is an incentive to Mexican nationals to engage in conservation by providing them with education and employment.

A portion of the money generated by the purchase of tags pays their wages. They sift through dead butterflies at the base of the trees looking for tagged monarchs. Tags also provide researchers with valuable data on monarch migration.

Corrections

In regards to a previous report on fossils, Bob O’Donnel pointed out two errors. Two unidentified U.S. citizens are selling area fossils, not the two American brothers as suggested in the article. The brothers do not sell their fossils and must be lauded for their contribution to paleontology. The brothers also were instrumental in setting up the fossil museum in Rock Glen Falls.

Also, a dendrite is manganese precipitating on the surface of a rock, not fossilization of prehistoric plant life.

SOURCE

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