Miraculous migration of the monarch
Lets say weve tasked NASA or the CIA to design a device weighing half as much as a paper clip. We want this device to be able to fly. In addition, we want it capable of navigating as far as 3,000 miles to a specific location, refueling on its own. Its doubtful it could be done with current technology. Yet that is exactly what nature long ago accomplished in the form of the Monarch butterfly (Danaus plexippus).
Right now, Monarchs have massed to peak numbers in our area on their way to wintering grounds south of Mexico City. Spurred by shortening days and cooling temperatures, its a journey unparalleled by any other butterfly in the world with a length more associated with birds or whales. NDSU entomologist Dr. Jerry Fauske says the insects will average about 35 miles a day during this trip south, depending on weather conditions. With favorable winds, the gossamer-winged beauties have been found soaring as high as 3,500 feet, Fauske says.
This is easily our most recognized butterfly. Bold orange with contrasting black wing veins make this one hard to miss. With a wingspan ranging from 3.5 to nearly five inches its one of the larger species in our area. Its found all over the US and into a large part of South America.
One plant genus represents the sole food source for the larval stage (caterpillar) of this insectmilkweeds (Asclepious). The female lays single eggs on the underside of various milkweed leaves. About the size of a pinhead, the egg will hatch in three to five days. The first meal is the egg case. After that its all milkweed leaves. The leaves contain toxic glycosides, or heart poisons, which are passed to the insect making them poisonous, even as adults. The caterpillar spends the day doing nothing but eating, resting and shedding its outer skin to allow for growth. Once ready, it will hang vertically from a twig or leaf and shed its skin for the last time. It has now entered the pupa stage of its life; whats called a chrysalis. Inside this lime green capsule it will magically metamorphose into the familiar adult in 10-14 days.
This process can be easily witnessed by planting a few milkweeds around the flower garden. The common milkweed is not recommended as this is a coarse and somewhat unsightly weed that spreads vigorously underground. Instead ask a nursery for swamp milkweed (A. incarnata), which is native to our area or showy milkweed (A. tuberosa), which is a striking orange flowered plant. Once established, female Monarchs will eventually find them.
Like all butterflies, the Monarch feeds with a long, tube-like proboscis or tongue, which it uncoils into nectar producing flowers. Many different plant species provide a food source for the adult. The Monarch feeding at your flowers today is storing fat in its abdomen. This is critical to a successful migration and its subsequent winter survival.
Monarchs west of the Rockies winter at more than 25 sites along the California coast. Perhaps the most notable is in Pacific Grove where local statutes levy a $500 fine for molesting a Monarch. East of the Rockies, the .5-gram adults navigate to only 13 mountain peaks along a narrow zone in Mexico. In fir trees here, they will mass in clusters of millions for protection from freezing temperatures. When exposed to extreme cold only the outer layers succumb, preserving the rest. In 1992 and again in 1995 an estimated five to seven million Monarchs died from snowstorms at their winter roosts.
In spring, the reverse trek is made. Most get as far as the Gulf States before reproducing. Their progeny (young) will continue the journey north, leapfrogging until they reach our area to carry on their lives. Ultimately, each adult that heads south in the fall is three to five generations removed from their ancestors who made the trip the previous fall, said Fauske.
We have but a few short weeks until the last adult is gone, normally about Sept. 20. After that any Monarchs you see will likely not beat the first frost. Until then, we can savor the waning numbers of these fascinating insects. And while we are bundled up enduring the winter months, know that on some far away mountain in Mexico, Monarch butterflies are doing the same thing.