Butterflies cross Sahara with the longest identified motion of bugs


Moroccan Painted Lady butterfly. Photo credit: Orio Massana

Scientists have found that species of butterflies found in sub-Saharan Africa can travel thousands of kilometers through the Sahara desert to Europe in good weather.

Impressive Painted Lady (Painted Lady) For the first time, it has been shown that butterflies can make more round trips (the longest known insect movement) of 12,000-14,000 km when the wet desert conditions aid in plant spawning. ..

The results of an international research team provide a better understanding of how insects, including pollen, pests and the diseases they transmit, may spread across continents in the future. Climate change Change seasonal conditions.

Professor Tom Oliver, ecologist and co-author of the study at the University of Reading, said, “The number of painted ladies in Europe varies widely and can multiply a hundredfold each year, but the conditions that caused this are unknown, and butterflies can reach Europe via the Sahara desert and the sea. The suggestion has not been proven.

“This study shows that this unlikely journey is possible and that certain climatic conditions leading up to the train season have a significant impact on the numbers of wildlife in the UK. We need strong international cooperation to show how we can protect such species across national borders. “

In addition to answering long-standing questions about butterfly migration, the results can also help predict the movement of other insects that infest humans, such as grasshoppers and malaria-carrying mosquitoes that are currently haunted in East Africa. There is sex.

Professor Oliver said, “It is fun to see the beautiful Painted Lady in European gardens, but climate change is also changing the number of invasive species that spread pests and diseases. The food shortage in East Africa has been influenced several times by climate change. The warming can be much more dramatic than initially thought. “

Maps showing the vast area of ​​Painted Lady have been found to move during each spring hike. Photo credit: Gao Hu et al

Painted Lady moves in the spring after the winter breeding season. Researchers learned about their movements through long-term monitoring data from thousands of trained volunteer recorders, as well as climate and atmospheric data from sub-Saharan Africa and Europe.

Studies published in the protocol of the National Academy of Sciences The journal found that the increase in vegetation in the savannah of Africa in winter and in North Africa in spring, coupled with favorable tailwinds, were the top three factors driving the number of immigrants to Europe.

Painted lady larvae feed on the leaves of plants that breed in the rainy winter conditions of the African savannah and Sahel regions south of the Sahara, causing the population to explode. They travel across the Sahara, and when North Africa also has damp green spring conditions, they allow further breeding and increase the number that reaches Europe across the Mediterranean.

Simulations by scientists have also shown that there is regularly favorable tailwind between Africa and Western Europe, which offers insects opportunities for transcontinental travel.

The team calculated that butterflies fly non-stop during the day to cross the Sahara, and need to rest at night and stop to eat nectar. This is similar to the pattern of songbirds moving in the night sky.

They came to the conclusion that butterflies have to fly up to 1-3 km above sea level in order to take advantage of the favorable tailwind, since a maximum self-flight speed of about 6 meters per second makes it very difficult to cross the Sahara.

Using similar butterfly species observations, the researchers calculated that Painted Lady had enough body fat to withstand 40 hours of non-stop flight after metamorphosis in the Sahara. Eat as much nectar as you can to cross it and keep topping it up.

The results can help to improve the prediction of which insect species will be found in different regions in the future due to climate change and how many they will arrive.

Painted Lady round-trip flight is the longest recorded butterfly

For more informations:
Gao Hu et al. , “Environmental Factors of Annual Population Fluctuations in Trans-Saharan Insect Immigrants” PNAS (2021). www.pnas.org/cgi/doi/10.1073/pnas.2102762118

Provided by
Reading University

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