After a 21-year study, an international team of researchers has presented strong evidence suggesting that the Painted Lady butterfly – previously believed to cross the Sahara desert and oceans to reach Europe – may certainly make the migratory journey of several thousand of kilometres.

Researchers from Spain, China, the UK and the Netherlands have found that fliers not only make the trip, but that they do so in greater numbers when wetter conditions in the desert help to make grow the plants on which they lay eggs. The results increase our understanding of how insects, including pollinators and disease-carrying pests, could spread between continents in the future in the context of climate change.

“It shows how the wildlife we ​​see in the UK can transcend national borders, and protecting these species requires strong international cooperation,” said Tom Oliver, conservationist at the University of Reading and co-author of a new study on butterflies that appears in the journal Proceedings of the National Academy of Sciences.

As her name suggests, the Painted Lady is a colorful creature. Its orange, black and white patterned wings can be spotted throughout North America, Central America, Africa, Europe and Asia. (The butterfly is the most common in the world, according to Colorado State University). It is part of the Nymphalidae family, which owes its name to the often hairy front legs of its members.

Painted Ladies are highly migratory butterflies, and the distance traveled during their annual migration is known to exceed that of successive generations of monarch butterflies, according to the Washington Post.

The study found that the migratory round trip of the Painted Ladies was approximately 7,450 to 8,700 miles (12,000 to 14,000 kilometers). Mass migration takes several generations of butterflies to achieve. To cross the Sahara, the butterflies must fly nonstop during the day and rest at night, making stopovers to feed on nectar, according to the study.

The researchers identified three main factors behind the number of butterflies migrating to Europe: increased vegetation in the African savannah during winter and in North Africa in spring, and favorable tailwinds. To take advantage of the winds, insects must also fly up to 2 miles above sea level.

To learn more about the movement of the butterflies, they used long-term monitoring data from thousands of trained volunteer loggers, as well as climate and atmospheric data from regions of sub-Saharan Africa and Europe.

After a winter breeding season, the Painted Lady migrates in the spring. First, painted lady caterpillars feed on the leaves of plants that thrive in wetter winter conditions in the savanna and Sahel regions of sub-Saharan Africa. This causes the proliferation of insects. Butterflies migrate through the Sahara, and when spring conditions in North Africa are also wet and green, there is more breeding, and the number of butterflies crossing the Mediterranean Sea to reach Europe increases.

Using observations of similar butterfly species, the researchers also calculated that the Painted Ladies had enough body fat after metamorphosis to withstand 40 hours of nonstop flight. The fair lady’s endurance is inspiring…and humbling, especially considering that the longest hike I’ve done today involved throwing a frozen pizza in the oven.