2014-08-31 10:53:21
Nature is full of wonders. Without a doubt, one of the most surprising is the Monarch butterfly (Danaus plexippus). This butterfly mainly lives in North America, although it is also found on other continents, including the distant Australian continent.
The Monarch is a beautiful butterfly, with large wings up to 10 cm in span, painted with intense orange and black bands. However, the true beauty of this butterfly is invisible to the eyes and it has only been possible to reveal it thanks to science. And science has revealed that this butterfly stars in one of the most impressive migrations in Nature, comparable to those of storks, although, being an insect, nothing can really compare to it.
Migration takes Monarch butterflies across North America, from southern Canada and northern US. to northern Mexico. There are thousands of kilometers that take months to travel. In fact, the migration lasts so long that none of the butterflies complete it. They all die along the way, but not before having given rise to new generations of butterflies that will complete it. In reality, completing the migratory cycle from north to south and back involves four generations of butterflies. The life of these butterflies is certainly a long journey.
Migration is truly daunting for an insect, even a flying insect. For a human being it would be comparable to migrating a distance greater than the perimeter of our planet at the equator, walking, or running, while we feed ourselves and have children and grandchildren along the way, which will represent the hope of one day completing the circumnavigation of the planet. , and to start again. Butterflies begin their migration north from Mexico in spring. Halfway, in the center of the North American continent, butterflies reproduce, then die. It is their children who reach the destination of this first part of the great migration: the places located in the northeast of the United States and southeast of Canada.
This second generation reproduces again when reaching these areas during the months of June and July. In this case, up to two new generations of butterflies can be produced. During the month of August, the butterflies begin their migration again towards the south, towards the areas from which their great-grandparents left. During this trip, butterflies enter a phase of their life called diapause, in which they do not reproduce, but their longevity is increased to six or seven months of life. Butterflies in diapause spend the fall traveling south, until they reach the places in northern Mexico where they will reproduce again, giving rise to a new generation that will begin the gigantic migratory cycle again.
strange compasses
This behavior is, to say the least, shocking for an insect. Definitely, powerful evolutionary forces must have operated in this species of butterfly to shape it. Furthermore, the same evolutionary forces must have acted to equip these insects with some means of orienting themselves on their kilometer-long migrations, as well as to know what each generation should do regarding where to go.
In previous studies, scientists had discovered that these butterflies use the position of the Sun, corrected by an internal clock, to orient themselves properly. However, butterflies continue to travel without becoming disoriented during cloudy days, when the Sun is not visible. This made researchers suspect that perhaps Monarch butterflies could also orient themselves using the Earth’s magnetic field, as other animals do, including pigeons and certain species of turtles.
Researchers from the Department of Biology and Biotechnology at the Worcester Polytechnic Institute, in Massachusetts, USA, address the study of this question by using a flight simulator for butterflies: an enclosure in which they can generate an artificial magnetic field and control their direction independently of the Earth’s magnetic field. The scientists captured several Monarch butterfly specimens and introduced them into their flight simulator. Through variations in the magnetic field to which they subjected the insects, the researchers confirmed that Monarch butterflies have in their antennas what we could consider a kind of compass that responds to the orientation of the Earth’s magnetic field, which allows them to travel, in generally, towards the equator, that is, it helps above all in orientation during the migration from north to south that occurs in autumn. Curiously, the operation of this compass depends on the presence of light of a wavelength typical of blue to ultraviolet light, typical of cloudy days, more frequent, in fact, in autumn. This type of light-dependent magnetic orientation mechanism does not appear to exist in other animal species.
This study, published in the prestigious journal Nature Communications, reveals another fascinating aspect of the biology of perhaps the most surprising butterfly on our planet, and opens the door to improving conditions to conserve this unique species that, of course, is found threatened by the massive use of pesticides in agriculture. Let’s hope that the surprising beauty that science reveals to us will help us take effective measures to protect this incredible migratory insect.
NEW WORK BY JORGE LABORDA.
It can be purchased here:
Chained circumstances. Ed. Lulu
Other works by Jorge Laborda
One Moon, one civilization. Why the Moon tells us that we are alone in the Universe
One Moon one civilization why the Moon tells us we are alone in the universe
The intelligence funnel and other essays
#Cienciaes.com #magnetic #orientation #Monarchs