This appears to be the very first mention of an invasive flatworm on the ISW...The Daily Yomiuri is reporting that land snails (Mandarina sp.) native to the Ogasawara Islands in Japan are being threatened by an introduced planarian (Platydemus manokwari). Native to New Guinea, Platydemus manokwari has been purposely introduced in some parts of the world as a control for the giant African snail (Achatina fulica). It has also been identified as a threat to native tree snails in Guam.
Bonus points to the Daily Yomiuri for using the scientific name of both the flatworm and the snail, and a tip of the virtual hat to Stop Aquatic Hitchhikers for posting about this story.