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Texas Invasive Species Institute

Texas Invasive Species Institute

New Guinea Flatworm

Platydemus manokwari

Class: Trepaxonemata
Order: Neoophora
Family: Geoplanidae

Platydemus manokwari

Source: https://doi.org/10.7717/peerj.297/fig-1


The New Guinea flatworm is a dark-brown predatory worm that was first discovered on the island New Guinea. As its name suggests, it is a flat, worm-looking invertebrate. Platydemus manokwari ranges from 1.6-2.6 inches. Both ends of the animal look similar, but the end with the head is narrower and has two eyespots. The underside of this animal is a pale tan and the upper-side has a faint stripe down it.  

Ecological Threat

This species is a predator of snails. It uses a white pharynx like a feeding tube and is able to drain snails completely. Despite seeming like harmless, slimy creatures, snails are an important link in the food chain and ecosystem. They have been imported in other nations to control the Giant African snail! A snail that can grow up to 7 inches in length! In several Pacific Islands, researchers have noticed a significant decrease, even extinction events, of many land snails. They have been documented to climb up trees following the snail trails of their prey.

This small flatworm also poses a threat to vertebrate animals like humans and other mammals by carrying parasites. Platydemus manokwari is known to be a paratenic host of the Rat Lungworm, Angiostrongylus cantonensis (please refer to our Species Page). Since the flatworms feed on snails that are often intermediate hosts of the Rat Lungworm, the flatworms are able to help spread the nematode parasite around. If they are infected with the parasite, they can increase an animals or humans ability to encounter the Angiostrongylus parasite.

 **The flatworm itself is not a parasite, but it has the potential to carry them. Please do not pick them up with your bare hands. Use gloves, a stick or disposable forceps**


Platydemus manokwari is a nocturnal worm. It has been observed to not only eat snails but also earthworms and isopods. They are also known to participate in gregarious attacks (ie: many attack the same prey).  


In 2015, the presence of the New Guinea flatworm was confirmed in Miami, Florida. Since it has a preference for sub-tropical areas and a tolerance for temperate zones, it could easily be throughout the Southeastern United States.

Native Origin

New Guinea

Current Location

U.S. Present: Texas, Florida and Puerto Rico

    In October 2018, TISI had collected specimens at Lamar State College campus, and it was confirmed as the of the New Guinea flatworm. It is well-established in the Austin, Houston and San Antonio metroplexes and surrounding counties. We are still actively tracking their distribution throughout the state.

U.S. Habitat: Since snails are widespread in various habitats, especially in subtropical and Tropical regions of the United States, the Southeastern United States are the most susceptible. Platydemus manokwari is already established in Florida and Puerto Rico.


Unfortunately, there are no known predators of this flatworm, so no bio control can be implemented for its management. Flatworms are thought to be susceptible to citrus oil and white vinegar mixtures to spray onto them directly. The normal strength calls for 2 ounces of citrus oil to 1 gallon of white vinegar. Spray that mixture directly on any flatworms, making sure you've sprayed the whole creature. This soft-bodied worm could be susceptible to salt, or slug repellent.

When purchasing slug repellent please be sure to buy the kind that is not harmful to domestic animals like dogs and cats; by making sure the repellent is made with "Iron Phosphate" and NOT "Metaldehyde".

We are actively tracking the distribution of this pest. To report this pest - please take a picture, provide location information and send an email to Ashley Morgan-Olvera, M.Sc. (arm001@shsu.edu) or Dr. Matthew McClure (matt.mcclure@lsco.edu).

 Please remember the flatworm itself is not a parasite, but it has to potential to carry them.

** Do not handle live flatworms bare-handed it is recommended that latex gloves be worn, or at least samples handled using a plastic bag. Hands should be washed in hot soapy water, and rinsed in alcohol or a standard hand disinfectant. Although meningeal angiostrongyliasis is not yet reported in the region where the slug has been detected, this a good preventative measure.**



de Beauchamp, P (1962). Platydemus manokwari n. sp., planaire terrestre de la Nouvelle-Guinée Hollandaise. Bulletin de la Société Zoologique de France. 87: 609–615.

Justine, J. L., Winsor, L., Barrière, P., Fanai, C., Gey, D., Han, A. W. K., ... & Philippart, D. (2015). The invasive land planarian Platydemus manokwari (Platyhelminthes, Geoplanidae): records from six new localities, including the first in the USA. PeerJ, 3, e1037.

Muniappan, R., Duhamel, G., Santiago, R. M., & Acay, D. R. (1986). Giant African snail control in Bugsuk island, Philippines, by Platydemus manokwari. Oleagineux, 41(4), 183-188.

Sugiura, S., & Yamaura, Y. (2009). Potential impacts of the invasive flatworm Platydemus manokwari on arboreal snails. Biological invasions, 11(3), 737-742.

Internet References




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