Two Asian praying mantises are spreading across Europe, and scientists warn they could threaten local wildlife
Two species of Asian giant praying mantises are spreading rapidly across Europe, prompting scientists to officially classify them as invasive threats to local wildlife.These fast-breeding predators are steadily moving north, aided by rising global temperatures and the warm conditions created by cities.
Researchers warn that the insects aggressively prey on important native pollinators such as honeybees, small, protected animals such as lizards and tree frogs, and even Europe’s native mantis species through lethal mating encounters.The official classification of the two species, Hierodula tenuidentata and Hierodula patellifera, as invasive alien species comes from a new study published in the open-access journal Orthoptera Research.
The study, conducted by Roberto Battiston of the G. Zanato Museum of Archeology and Natural Sciences, reveals a highly successful environmental invasion that has received little scientific attention until now.
Climate change is pushing spread north
Although these insects have been present in Europe for about a decade, their numbers have increased sharply in recent years in both mainland Europe and the Mediterranean region. Warmer city environments and general climate change allow them to spread into areas that were previously too cold for them to survive.
“They’re moving northward more and more, thanks to climate change,” Battiston said, adding that people are now regularly spotting established populations in parks and gardens. Because these mantises are large, colorful, and eye-catching, many people consider them an interesting garden insect rather than a potential environmental threat.“This study was born to give people those answers and to develop strategies to contain them,” Battiston added.
Rapid reproduction gives them an advantage
The success of this Asian mantis comes from its adaptability and extremely high reproductive rate. Both species spend most of their lives hidden in trees and shrubs, where they are very effective hunters.One egg case laid by an invading female produces about 200 young. This is nearly twice the number of the native European mantis, Mantis religiosa. Young invasive praying mantises are also much less likely to eat each other than native species, allowing many more of them to survive into adulthood.This rapid population growth has become a serious threat to local wildlife. Large invasive females release pheromones that attract native European males. When native males attempt to mate with them, they are often hunted and eaten, reducing the breeding numbers of native species.Invasive praying mantises also prey on many other animals. They feed on important pollinators such as honey bees and pose a major threat to small, protected animals such as tree frogs and lizards.
This is particularly worrying for the Mediterranean islands, which are home to many unique plant and animal species found nowhere else in the world, the researchers said.
Two Asian praying mantises are spreading across Europe, and scientists warn they could threaten local wildlife
How cities and house cats share
Man-built cities have accidentally created ideal conditions for these invasive insects. Urban areas produce additional warmth, known as the urban heat island effect, allowing praying mantises to stay active and hunt later in the fall and winter than usual.In addition, insect hotels built to support native insects are now used by the Hirudula mantis as excellent hunting grounds.The study also found an unexpected link with domestic cats. The data showed that free-roaming cats are the main vertebrate predators of these invasive insects, accounting for 45 percent of all recorded successful attacks on them.However, cats do not solve the problem. They cannot distinguish between invasive Asian praying mantises and native European praying mantises.
As a result, they are also killing off native praying mantises, which are already under pressure from increased competition in suburban areas.
Search for egg cases during the winter
To monitor and slow the spread of these insects, researchers asked the public for help through a major citizen science project.“My colleagues William Di Pietro and Antonio Fasano (GRIO) were able to create a massive citizen science project and collect more than 2,300 reports from enthusiasts and citizens,” Battiston said.
“Citizen science is an essential tool not only for monitoring but also for raising awareness and informing people in an active and participatory way about these issues.”Environmental groups say people can help during the winter, when trees and shrubs lose their leaves. Without leaves, mantis eggs, called oothecae, are much easier to spot on bare branches. The brown, sponge-like egg boxes are usually about 2 to 3 centimeters in size.Although these egg cases can be safely removed to prevent new praying mantises from hatching in the spring, Battiston cautioned that people should first ask an expert to identify the species. This helps ensure that the eggs of native mantis species that are already struggling in Europe are not destroyed.
