Butterflies may be fragile and tiny, however, there are some of them which are heroic migrators. Yes, the North American monarch butterfly is one of the few insects that can travel long distances, flying up to 2,500 miles each year from the United States and Southern Canada to Mexico.
Well, here’s another interesting story. Just like the monarch, the Painted Lady (Vanessa cardui) turns out to be an epic migrator with similar flying characteristics. It now boasts its ability for flying the farthest of all butterflies.
A study published in the journal Biology Letters says that this colorful wanderer performs an annual migration between Europe and North Africa, covering nearly 7500 miles (12,000 km). It crosses the Sahara Desert twice to exploit the resources and favorable climates on both sides of the desert. It’s the longest ever flight recorded in butterflies to date.
Researchers from the Institut de Biologia Evolutiva in Barcelona, Spain found that the Painted Lady endures annual trans-Saharan circuits like a few birds. The researchers write, “Very few insects are known to endure annual trans-Saharan circuits, but the Painted Lady butterfly is an exception.”
In earlier studies, it was found that the painted lady butterflies travel from Europe to tropical Africa during the autumn, crossing the Mediterranean Sea and the Sahara Desert. Nevertheless, the fate of these migrants remained unknown. Roger Vila, one of the authors of the study said, “Our hypothesis was that the species initiates a reverse northward migration towards Europe in spring, thus completing a regular migratory cycle.”
To reach this conclusion, the team studied the natal origin of the butterflies arriving into the Mediterranean region during the spring season. They analyzed the stable hydrogen isotopes of the butterflies sampled in Morocco, Andalusia, and Catalonia in Spain, Crete, Egypt, and Israel.
An isotope refers to each of two or more forms of the same element that contain equal numbers of protons but different numbers of neutrons in their nuclei. The proportion of hydrogen and its stable isotope in water depends on the location. When absorbing water, the plants maintain this proportion. The proportion then remains in the caterpillars that feed on these plants, and finally, in adult butterflies.
After performing a study of the hydrogen stable isotopes found in the wings of adult butterflies, the researchers could find where they developed as caterpillars.
Gerard Talavera, who led the research, said, “It is difficult to study the movement of insects by means of observations, marking or radio tracking since there are millions of individuals and they are very small. Therefore finding out where a butterfly grew up before undergoing the metamorphosis by means of stable isotope analysis turns out to be extremely useful. It feels like magic.”
The studies reveal that most of these creatures stay in the Afrotropics during winter and those recolonizing the Mediterranean are possibly their offspring.
This infers that the distance traveled by the successive generations annually may reach nearly 7,500 miles, including the crossing of the Sahara Desert twice.