Fall is here, and resident local plants and animals are preparing for colder weather. For many creatures, these preparations involve “getting out of town” and heading for warmer climes.
Birds usually come to mind when we think of migratory animals. However, some insects have a migratory instinct. Most notable among these are the Monarch butterflies (Danaus plexippus). These striking, black and orange insects are found locally throughout the warm months of the year.
The female Monarch has more prominent black markings, while the male has more orange coloration. He also possesses two black “dots” on his hind wings. These are groups of specially adapted scales which release pheromones which attract the female of the species. Although their coloration is attractive for us to look at, the combination of orange and black serves as a warning to potential predators. These hues advertise the bad taste of the insect, which are a result of it’s diet of Milkweed plant leaves.
The lifecycle of the Monarch Butterfly is very closely associated with this particular plant. The female butterfly seeks out the Milkweed specifically for laying her eggs. You can see an image of a tiny Monarch egg on a Milkweed leaf among the photographs that accompany this blog. When the caterpillar hatches from the egg it begins to feed on the Milkweed. The larva accumulates substances acquired from the plant which make it distasteful to predators.
These substances remain in the adult butterfly as well and imbue it with a flavor distasteful to birds and other would be predators. The caterpillar is strikingly patterned with black, white and yellow stripes. There’s no attempt at camouflage since any bird that tries to eat one of these larva will most likely regret the experience!
In it’s next stage of development, the Monarch becomes a beautiful chrysalis. With it’s jade green color and flecks of metallic gold, this structure is truly exquisite. Within the chrysalis, which is attached to a suitable twig of a plant, the caterpillar makes it’s transformation into a butterfly. The adult emerges from the chrysalis with a rather rumpled appearance, but it expels excess fluids, and slowly expands it’s graceful wings. These wings will enable the butterfly to undertake it’s amazing migration.
When fall arrives populations of Monarchs from points north join our local stocks on their way south. It is at this time of year when they are encountered in the greatest numbers. There are many excellent locations for viewing Monarch Butterflies as they pass through our area is along Long Island’s north and south shore beaches. Take a stroll on a sunny day in Sunken Meadow State Park, Nissequogue River State Park, or Callahan’s Beach and you are sure to see these boldly colored members of the Lepidoptera family of insects winging their way south, or pausing at a clump of goldenrod flowers for a refreshing sip of nectar. Many of the photographs that accompany this article were taken by me on just such a stroll, at Sunken Meadow. During that walk in early October I saw dozens of Monarch butterflies, and several other butterfly species.
The Monarchs that were sipping from goldenrod that day needed the nectar to maintain their strength, as they have an arduous journey ahead. If they survive, they will travel thousands of miles, all the way to a particular, special region of Mexico.
Though small and fragile looking, the Monarch Butterflies are accomplished fliers. They may fly as high as 10,000 feet, and can travel as fast as 30 miles an hour. Ultimately they reach the Oyamel Fir tree forests of Mexico, where they congregate in vast numbers. The butterflies will often collect in such great quantities that they drape entire trees in an orange and black coat of wings! The ecosystem in which these forests are found are essential to the butterflies’ survival, as they provide consistent, cool, moist conditions and shelter. This allows the Monarchs to survive the winter. Without access to this special habitat, these migratory populations of Monarch butterflies would be severely impacted. Unfortunately illegal logging is rampant in these forests, and is indeed negatively affecting the Monarch Butterflies’ survival.
These butterflies do not make a “round trip” back to their starting point. Instead, the migration takes place through successive generations. The females lay eggs, and the adults from the next generation move northward, reproducing as they travel. Finally the most northerly generation repeats the cycle of migration, beginning to make the flight to the same forests in Mexico that their great, great, grandparents started from the previous winter.
In addition to the Monarch Butterflies, another butterfly species known as the Common Buckeye (Junonia coenia) is also on the move. These insects are smaller than the Monarch. They are brownish overall, with attractive orange, tan, and vivid blue spots on their wings. These handsome butterflies are also on the way south. Unlike Monarchs, they do not congregate in one location, but disperse throughout our southern states. You can see these beautiful butterflies feeding on flowers such as Seaside Goldenrod (Solidago sempervirens) along our Long Island coastlines.
The migrations of wildlife at this time of year are an amazing phenomenon. We are privileged especially to witness the Monarchs passage through our area each Fall. I hope you get a chance to visit our nearby parks and enjoy this natural spectacle. See you outside on the trails!