New Guinea Flatworm

Fast Facts

Latin name: Platydemus manokwari

Notable feature: Invasive Non-Native Species (INNS) not yet found in the UK

Conservation Status: Not Evaluated

Where in the UK: This Invasive Non-Native Species (INNS) has not yet been found in the UK

New Guinea Flatworm (Platydemus manokwari) © S.Sugiura


The New Guinea Flatworm (Platydemus manokwari) is a non-native species, originating from as the name would suggest New Guinea; it is considered invasive as it is spreading rapidly and its presence is impacting native wildlife across Europe.  It has not yet been recorded in the UK.

The New Guinea Flatworm has a brown or black body with a pale stripe running down the middle; the underside is pale. The long, snout-like head has two eyes that sit back from the pointed tip.  This flatworm measures between 4-6cm in length.

The New Guinea Flatworm was recorded in a hothouse in Caen, France, in 2014 – the first record in Europe. Concerns are increasing on its potential spread and what can be done to stop it arriving in the UK.

    • Size: 4-6cm in length
    • Life span: Undetermined
    • Diet: The New Guinea Flatworm’s diet includes land snails, earthworms (such as the Lob Worm aka Common Earthworm) and other invertebrates.  It has had significant impact on native snail populations in places it has been introduced
    • Reproduction: The New Guinea Flatworm reproduces sexually.  Producing cocoons that contain 3 to 9 embryos which will hatch after approximately 8 to 10 days. Juveniles reach maturity approximately three weeks after hatching.
    • When to see:  Mostly nocturnal, but can be found in potted plants, under rocks, and in leaf litter and other dark undisturbed areas.
    • Population Trend:  Not yet recorded in the UK
    • Threats: There are no recorded natural enemies and no biological or pesticide control methods for non-native flatworms, the key control measure is to prevent their introduction to new areas.
    • Fun Fact:  The New Guinea Flatworm is among the “100 World’s Worst Invader Alien Species” – the only flatworm on the list.

As with other flatworm species the New Guinea Flatworm is likely to be distributed via the movement of plants and growing media in the horticultural trade.

How you can help: 

Buglife is working to increase awareness of Invasive Non-Native Species (INNS) and their, often detrimental, impacts on our native wildlife and habits.  Working with other organisations to highlight how biosecurity is everyone’s responsibility and that we can all play our part.

Join a recording scheme and log your flatworm finds – send any records/sightings to our flatworm recording scheme – Potwatch!

Follow our biosecurity guidance (at the bottom of the linked page) on flatworms to help prevent their spread and destroy any non-native flatworms that you find.

Do remember that we rely on donations to continue our work.  If you have searched, found and learnt about our incredible invertebrates on our website, please do consider Making a Donation, Becoming a Member or maybe even making a purchase in our shop.  For more ideas on how to support our work find out how to Get Involved.  Thank you 🕷