Migration of the monarchs underway
This spring was the warmest in 117 years of record-keeping and the warmest 12-month period ever recorded in the United States.
In response to the warm conditions, plants and insects made early appearances. Plants bloomed from a modest two weeks earlier than normal to as much as six weeks earlier than in previous years.
Most insects, including the monarch butterfly, kept pace with the early blooming. Many monarchs made the trip north from Mexico two to three weeks earlier this spring.
The early arrival to their northern breeding ranges raises the possibility of a large fall monarch migration and perhaps the last big migration of this decade.
Climatologists are predicting future summers to be hotter and accompanied by extensive periods of drought. If these predictions come true it will tragically affect monarchs and many other wildlife species.
The monarch is one of the most common butterflies and probably the one butterfly species that most people can identify. Monarchs belong to the milkweed family, Danaidae. The family includes the queen and viceroy butterflies.
Monarchs are the only butterflies that truly migrate. Some monarchs travel up to 80 miles a day while migrating approximately 2,000 miles to the mountains of Mexico.
They spend the winter on tree trunks and branches with hundreds of millions of other monarchs that left their summer homes before the cold northern fall and winter temperatures.
These long-distance travelers rely on stored body fat to survive the winter. Most monarchs mate before they leave Mexico on the way to their northern home ranges. This migrating brood lives about eight months.
The migrators produce offspring that emerge during the summer and live about two to three weeks. This is just long enough to mate and lay the eggs that will develop into this year's migrating brood.
The female monarch lays about 400 to 600 eggs, one at a time on the leaves of the milkweed plant. Pinhead-sized eggs hatch in three to five days. The tiny caterpillars, also called larvae, eat their egg cases before gorging themselves on the milkweed leaves.
As the caterpillars eat and grow, they shed their outer skin five times. After two weeks, the two-inch long caterpillars are about 3,000 times their original weight. This would be equivalent to a 150-pound person weighing 450,000 pounds after two weeks of binging.
After satisfying its hunger, the satiated caterpillar crawls to the underside of a twig or leaf where it spins a tiny silk button. Hanging from the button in a "J"-shape, it sheds one more time, revealing a green pupa case called a chrysalis (moths spin a cocoon).
As the chrysalis hardens, a pattern of gold dots begins to form on the upper surface. It is during this 10- to 14-day pupal stage that one of the true miracles of nature takes place. The green and black striped caterpillar emerges as a beautiful adult monarch butterfly.
When the adult emerges from its chrysalis, it hangs upside down until enough fluid is pumped from its body to its wings. Finally, the wings unfold, harden and become ready for flight. Adults feed on flower nectar.
Late summer changes in length of daylight and temperature trigger the beautiful and graceful monarch butterflies to begin swarming together to form huge migratory flocks. An estimated 250 million or more monarchs flee the cold northern weather by migrating to roosts in the mountain fir forests west of Mexico City.
Allentown is located at about 40.6 degrees north latitude. According to the Monarch Watch website, an organization that monitors monarch migrations, the peak time for observing monarchs in the Lehigh Valley is from early September to the end of the month.
Nature centers host monarch-tagging programs before the monarch flocks leave the area. Each tag is about the size of a thumbtack head. Each tag has three letters and three numbers.
The tagging program compares the area of capture and tagging to the point of recovery for each tagged monarch. Data from the recovered monarchs is used to determine the migration routes taken, the possible influences of weather on the migration and the survival rates.
Many questions remain about the Monarch's migration. Tagging programs and follow-up studies will hopefully clear up the mysteries of the migration.
The Bertsch-Hokendauqua-Catasauqua Watershed Association will tag monarchs during a hike Sept. 15, which is "Know Your Watershed Day," on the Mary Immaculate Center property in Allen and Lehigh townships, Northampton County.
To register, contact Bob Hosking, bobhoskingjr@ gmail.com, 610-262-7680.
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Email comments and questions to: bbbcole@ enter.net. To schedule programs, hikes and birthday parties, call 610-767-4043.
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