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A veritable monarch motel
Eyes on West Meadow
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September 09, 2009 | 03:21 PM
The days are already growing shorter, and there is a noticeable chill in the morning and evening air. Autumn is just around the corner. I eagerly await the arrival of monarch butterflies at West Meadow Beach, where many will stop to feed and rest before continuing their journey south. For the monarch butterfly, West Meadow Beach is a veritable monarch motel.
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The monarch life cycle consists of four stages, each of which is quite attractive. Adult females lay eggs, which look like tiny lined footballs, on common milkweed (Asclepias syriaca). The emerging caterpillars, striking black with white and yellow stripes, quickly grow to nearly 3 inches on a diet of milkweed leaves, flower buds and milky juice. Milkweed is toxic, but monarch caterpillars are adapted to feed on it. The toxins are incorporated into their tissues, making them unpalatable to birds and other animals that would otherwise consume them. Thus monarch butterflies have built-in protection from predators.
Once full grown, a caterpillar transforms into a beautiful gold-studded, sea-foam green, translucent, barrel-shaped chrysalis — the pupa stage. Inside the chrysalis, the pupas undergo metamorphosis, a complete body change, to become the stunning black and orange butterflies you see each fall. The entire process takes about a month.
Whereas most insects complete their life cycle in a single locality, monarch butterflies are unique in that many undergo long migrations, flying as far as 2,500 miles from Canada and North America to Mexico and southern California, and back to the southern United States. Monarchs east of the Rocky Mountains migrate south to the Transvolcanic mountain range in central Mexico where they winter, roosting by the tens of millions in oyamel fir trees. Returning butterflies mate and lay eggs along the way and then die. The new generations replace the old and continue the journey north. It is the fourth generation of monarchs that makes the long migration south each fall. It is amazing that these tiny, 0.02 ounce creatures can travel such great distances on fragile wings, sometimes over open water.
Adult monarchs use their proboscis, a tubular feeding structure, to extract nourishment and water from the nectar of seaside goldenrod, found in large quantities along the marsh, dunes and beach at West Meadow. It grows to an average height of about 3 feet; has long, fleshy leaves; and many one-sided clusters of bright yellow flowers. By the way, goldenrod should not to be confused with hay fever causing ragweed. Take a walk along Trustees Road this fall and you'll see the abundant goldenrod here. Keep an eye out for monarchs resting and feeding upon it. Spot one and you can determine if it is a male or female. Males have tiny dots (scent glands) on their hind wings. Females have thicker veins and lack the dots.
This season I will be tagging and counting monarchs that stop over at the beach on their way to Mexico. Scientists use tagging recovery data to determine mortality en route, estimate numbers of wintering monarchs, and it may be helpful in learning how monarchs navigate.
As a triathlete, I know the importance of eating well, staying hydrated and resting before a race. West Meadow Beach provides an ideal location for monarch butterflies to stop, rest and refuel before continuing their grueling journey south.
If you would like to witness the spectacle of the monarch migration at West Meadow Beach, please join me for a family walk (ages 6 and up) on Saturday, Sept. 26, from 1 to 2:30 pm. Call 751-7863 to register. I hope to see you there.
Eileen Gerle is the Brookhaven Town environmental educator at West Meadow Beach.
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