Two giant Asian praying mantis species are rapidly spreading across Europe, leading scientists to officially classify them as invasive threats to native wildlife.These fast-breeding predators are increasingly moving north, helped by rising global temperatures and warmer conditions created by cities. Researchers warn that the insects are aggressively preying on important native pollinators such as bees, protected small animals such as lizards and tree frogs, and even Europe’s own native mantis species through deadly mating encounters.The official classification of two species, Hierodula tenudentata and Hierodula patellifera, as invasive alien species comes from a new study published in the open-access Journal of Orthoptera Research. Led by Roberto Battiston of the Museum of Archeology and Natural Sciences “G. Zanato”, the study reveals a highly successful ecological invasion that had until now received little scientific attention.
Climate change drives northward spread
Although these insects have been present in Europe for about a decade, their numbers have increased rapidly in recent years in both mainland Europe and the Mediterranean region. Warming city environments and overall climate change are allowing them to spread into areas that were once too cold for them to survive.“They’re moving north faster because of climate change,” Battiston said. He said people are now regularly seeing established populations in parks and gardens. Because these mantises are large, colorful, and attractive, many people view them as an interesting garden insect rather than a potential environmental threat.“This study was born to give people the answers they want and to develop strategies to prevent them,” Battiston said.
They benefit from reproducing faster
The success of these Asian mantises comes from their adaptability and their extremely high reproductive rates. Both species spend most of their lives hiding in trees and bushes, where they are highly effective hunters.One egg laid by an aggressive female produces about 200 young. It is approximately twice the size of the native European mantis, Mantis religiosa. Young invasive mantises are much less likely to eat each other than native species, allowing very few of them to survive to adulthood.This rapid population growth is becoming a serious threat to local wildlife. Large aggressive females release pheromones that attract native male European mantises. When native males try to mate with them, they are often captured and eaten, reducing the breeding numbers of the native species.Aggressive mantises also prey on many other animals. They eat important pollinators such as bees and pose a serious threat to protected small animals such as tree frogs and lizards. The researchers said this is particularly worrisome for the Mediterranean islands, which are home to many unique plant and animal species found nowhere else in the world.
Two Asian praying mantises are spreading across Europe, and scientists warn they may now be endangering native wildlife
How are cities and domestic cats involved?
Man-made cities have accidentally created ideal conditions for these invasive insects. Urban areas produce excess heat, known as the urban heat island effect, allowing praying mantises to remain active and hunt much later than usual in autumn and winter.Additionally, insect hotels built to support native insects are now being used by Hirodula mantises as excellent hunting sites.The study also found an unexpected association with domestic cats. The data showed that free-roaming cats are the main vertebrate predators of these aggressive mantises, making up 45 percent of all successful attacks recorded on them.However, cats do not solve the problem. They cannot tell the difference between the invasive Asian mantis and the native European mantis. As a result, they also kill native mantises, which are already under pressure from increased competition in suburban areas.
Looking for egg boxes during winter
To track and slow the spread of these insects, researchers asked the public to help through a large citizen science project.“My colleagues William Di Pietro and Antonio Fasano (GRIO) have managed to set up a massive citizen science project and collect over 2,300 reports from enthusiasts and citizens,” Battiston said. “Citizen science is a fundamental tool not only for monitoring but also for raising awareness and informing people about these issues in an active and participatory way.”Environmental groups say people can help during the winter, when trees and shrubs lose their leaves. Without leaves, mantis egg cases, called oothecae, become much easier to see on bare branches. These brown, spongy egg boxes usually measure about 2 to 3 centimeters.Although these egg cases can be safely removed to prevent new mantises from hatching in the spring, Battiston cautioned that people should first ask an expert to identify the species. This helps ensure that they do not accidentally destroy the eggs of Europe’s already struggling native mantis species.