Invasive Asian Giant Mantis Reaches Croatia's Mljet National Park

Authorities at Mljet National Park, on one of the most forested islands of the Croatian Adriatic, have recorded the Asian giant mantis within the park. As reported by Total Croatia News on 12 November 2026, citing Index and the park's own statement, the park says that changing weather conditions are making it easier for this species to survive across Europe, and that it has spread through the eastern Mediterranean in recent years, Croatia included.

The park has set out how visitors and residents can tell the newcomer apart from the native common praying mantis, Mantis religiosa. The Asian giant mantis has a noticeably larger body and carries a white or yellowish spot on its front wings. Its body is mostly green, though it can show brown or yellow shades. Unlike the native species, which is usually found in grass and low vegetation, it tends to stay high in the tree canopy, which makes it harder to spot and to count.

Park staff are careful about what is known and what is not. The mantis feeds on other insects, but its long-term effect on local populations of other species has not yet been established. Only over the coming period, the park says, will it be possible to judge what consequences, if any, its presence will have for the island's ecosystem.

The wider European evidence suggests the question deserves close attention. In July 2026, a study in the Journal of Orthoptera Research led by Roberto Battiston formally designated two Asian mantises found in Europe, Hierodula tenuidentata and Hierodula patellifera, as invasive alien species. The researchers reported that the insects have been present in Europe for about a decade, that their populations have grown sharply in Mediterranean and continental regions, and that warmer conditions are helping them push further north. The Mljet report does not say which of the two species was seen on the island.

According to that study, each egg case produces on average about 200 young, nearly twice as many as the native European mantis, and the nymphs are less likely to eat one another, so numbers can rise quickly. The invasive mantises prey on a wide range of animals, including pollinators such as honeybees and protected small vertebrates such as tree frogs and lizards. Invasive females also attract native males, which are then eaten, adding pressure on the native species. The authors singled out Mediterranean islands, with their many endemic invertebrates and vertebrates, as places where the risks most need assessing.

That makes Mljet a meaningful place for an early record. The western part of the island has been a national park since 1960, with dense Aleppo pine and holm oak forest around its two saltwater lakes. Canopy-dwelling predators are exactly the kind of species that can go unnoticed in such a landscape until their numbers are already established.

The practical tools are modest but real. Researchers behind the July study built a citizen-science network that gathered more than 2,300 sightings, and they point out that the brown, spongy egg cases, about 2 to 3 centimetres long, are easiest to find on bare branches in winter. They advise consulting a specialist before removing any, so that native mantis eggs are not destroyed by mistake. For Mljet, the first step is the one the park has already taken: telling people what to look for and asking them to report it.

Why it matters

The record comes at the point where acting is cheapest. The park says the mantis's impact on local species is not yet known, and that uncertainty is the window in which monitoring, public reporting and the winter search for egg cases cost the least and leave the most options open; once a canopy predator that produces around 200 young per egg case is established on an island, containing it becomes far harder.