It’s no hammerhead shark, but the hammerhead flatworm has become a real menace in France. Or at least a menace to earthworms, as Earther reports.

Believed to be an invasive species from Asia, the hammerhead flatworm was only recently recorded in France, as is documented in a new study (titled "Giant worms chez moi!") published in the journal PeerJ. However, based on reports, photographs, and videos sent in by citizens across the country, scientists determined the pests have gone undetected for nearly 20 years. This came as a shock, especially because the worms can measure more than a foot in length.

In recent years, three species of the carnivorous worm have quietly taken over French gardens and have even been spotted in metropolitan areas. Some species immobolize their prey with tetrodotoxin, the same powerful neurotoxin that makes pufferfish so poisonous. The worms secrete digestive enzymes, allowing them to dissolve earthworms and slugs their size.

Jean-Lou Justine, co-author of the study, says their eating habits are a concern. "Earthworms are a major component of the soil biomass and a very important element in the ecology of soils," Justine tells Earther. "Any predator which can diminish the populations of earthworms is thus a threat to soil ecology."

Archie Murchie, an entomologist who was not involved in the study, told The Washington Post that the worms will continue to spread in step with global trade. The worms were also seen in overseas French territories, including one worm with a blue-green hue that is probably a newly detected species, Murchie tells the newspaper.

[h/t Earther]