Swiss study: insects mainly migrate at midday and dusk

Many migrating insects provide vital ecosystem services such as pollinating plants. Keystone / Gian Ehrenzeller

A study led by the Swiss Ornithological Institute in canton Lucerne has shown that, throughout Europe, insects tend to prefer moving around midday or dusk.

Understanding such migratory movements is of great importance both for the protection of insects as well as their management, study author Birgen Haest told the Keystone-SDA news agency on Tuesday. For example, the findings, published in the “Philosophical Transactions” scientific journal, make it possible to determine the optimal time for the use of insecticides.

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At certain times of the year, trillions of insects travel, at altitudes of up to several hundred metres, to other locations, Haest explained. Some insects migrate hundreds to thousands of kilometres.

“An insanely large biomass is moved in this way,” said Haest. Many of the insects provide vital ecosystem services such as pollinating plants. Others are pests which threaten biodiversity, cause considerable economic damage or pose a threat to human health.

Studying small insects is difficult

Against the backdrop of insect extinction and the suspected effects further up the food chain, a better understanding of the movement patterns of migratory insects is urgently needed, the researchers say in the study.

“Little is known about these migratory movements,” said Haest. This is because studying insect migration is not an easy endeavour. “The insects fly high in the air and are very small,” the researcher said. Traditional methods would quickly become too costly and impractical for long-term, time-specific and geographically-distributed data collection.

For their study, the researchers recorded insects with radar devices between March and October 2021. The radar network was placed in 17 locations, from south-west France to Helsinki.

“To our surprise, we found that the migration peaks were the same across Europe,” said Haest. This shows that the insects probably use daylight as their means of orientation.

Adapted from German by DeepL/dkk/dos

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