Praying mantises have long captured human imagination across cultures, symbolizing anything from spiritual guides to omens of misfortune. Beyond folklore, indigenous mantis species serve as vital bioindicators of thriving, diverse ecosystems.
However, scientists now caution that two mantis species native to Asia are emerging as a significant danger to Europe’s indigenous wildlife.
Asian Giant Mantises Formally Listed as Invasive Alien Species
A recent study in the open-access journal Journal of Orthoptera Research has officially classified two Asian mantis species established in Europe, Hierodula tenuidentata and Hierodula patellifera, as Invasive Alien Species (IAS). The classification stems from research led by Roberto Battiston of the Museum of Archaeology and Natural Sciences “G. Zannato,” which investigated the ecological impact of these species—a topic previously overlooked by science.
Battiston notes the insects have inhabited Europe for about ten years, yet their numbers have surged across Mediterranean and continental regions in recent years.
“They are advancing northward progressively, facilitated by climate change,” Battiston states, noting that residents frequently report established populations in parks and gardens. Because these mantises are sizable and striking, the public often welcomes them rather than recognizing a potential ecological threat.
“This study arose to provide clarity and to formulate containment strategies.”
Reasons Behind Their Rapid Proliferation
Both Hierodula tenuidentata and Hierodula patellifera are sizable, versatile predators that inhabit trees and shrubs. They also exhibit extraordinary reproductive output. A single egg case yields roughly 200 offspring—nearly double that of the native European mantis (Mantis religiosa). Additionally, their nymphs seldom engage in cannibalism, enabling swift population growth.
This success poses grave consequences for local fauna. Invasive females lure native male mantises, which attempt mating and are consumed, depleting regional populations. They also prey on diverse native creatures, including essential pollinators like honeybees and protected small vertebrates such as tree frogs and lizards.
Scientists emphasize the need to evaluate risks on Mediterranean islands, which host numerous endemic invertebrate and vertebrate species found nowhere else.
Domestic Cats, Urban Areas, and Climate Influences
A notable discovery is that domestic cats are the primary vertebrate predator of these invasive mantises, responsible for 45% of documented predation incidents.
Battiston observes that while cats may suppress invasive mantis numbers, they cannot differentiate between invasive and native species. Free-roaming cats also hunt European mantises, which already face competitive pressure from the newcomers and are diminishing in many peri-urban settings.
Human development further aids their expansion. Urban and suburban environments offer optimal habitats, enabling Hierodula mantises to exploit features like insect hotels as efficient hunting grounds. Urban heat islands also prolong their activity into colder months, extending both survival and range beyond natural limits.
Citizen Science as a Tool to Curb Spread
To better comprehend and mitigate the expansion, researchers are engaging the public.
“My colleagues William di Pietro and Antonio Fasano (GRIO) have launched an extensive citizen-science project, compiling more than 2,300 reports from enthusiasts and citizens. Citizen science is essential not only for monitoring but also for raising awareness and actively engaging the public on these matters.”
Experts note that public action can extend beyond reporting. In winter, when foliage is absent, the mantises’ oothecae—brown, spongy egg cases roughly 2 to 3 cm long—become visible on branches. While these can be removed harmlessly, Battiston advises consulting a specialist first to avoid destroying eggs of native mantis species.
Safeguarding Europe’s Native Biodiversity
The proliferation of these Asian mantises illustrates how human activity and climate change erode natural barriers once limiting invasive species. As these adaptable predators spread across Europe, researchers stress that awareness, citizen science, and targeted conservation are crucial to preserving the continent’s indigenous biodiversity.
