France is being invaded by weird predatory flat-headed worms, posing a threat to local wildlife.

These alien-looking worms, called hammerhead flatworms, have crept into gardens across the country and French territories. The study gathered reports of these strange creatures that grown up to 40cm in length.

The worms were discovered by amateur naturalist Pierre Gros in his garden outside Paris. He emailed a picture to Jean-Lou Justine, a zoologist at the Muséum National d’Histoire Naturelle in Paris. Justine initially believed the picture as fake, but Gros persisted and kept sending in more images of the huge worms of different species all in his garden.

“The man is bringing back worms from his travels and he pretends he finds them in his garden!” Justine told The Washington Post about the images.

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However, what's more interesting is that these creatures are not new, as they have gone totally unnoticed regardless of this big size. Published in the journal PeerJ, the research notes that these worms have occupying France for nearly two decades. Apart from France, these alien worms have also been discovered everywhere from England to French colonies in the Caribbean, reported Business Insider.

Regarding going unnoticed, baffled Justine told The Post, “It is France! It is supposed to be a developed country. We have a lot of scientists; we have universities everywhere.”

Moreover, all the species of these worms are predators and pose a serious threat to other small creatures living in the soil and also the ecological processes. For now, researchers are just working on to know more about these giant predator worms.