P. manokwari measures about five centimeters (two inches) long by five millimeters (a fifth of an inch) wide.
The back is black olive in color, with a pale white belly where its mouth is located. The head is elongated, with two prominent black eyes.
It has been introduced, sometimes deliberately, in more than 15 countries and territories in the Pacific.
Biologists are alarmed by its appetite for snail.
The worm can even pursue gastropods up tree trunks -- and when supplies of snails run out, it can tuck into other soil species, including earthworms.
The worm's ancestral habitat is the mountains of New Guinea, at altitudes of 3,000 meters (10,000 feet) and above, where the temperature is moderate.
Tests have shown the worm can survive temperatures down to 10 degrees Celsius (50 degrees Fahrenheit), which gives it a good chance of surviving in temperate, snail-friendly parts of Europe.
"Platydemus manokwari represents a new and significant threat to biodiversity in France and Europe, which hosts hundreds of species of snails, some of which are endangered and protected," said PeerJ, a publisher of peer-reviewed studies.