Flatworms, Invasive Worms

the flatworm has been reported several times in comments on the blog (on the article about earthworms or on the article devoted to Colorado potato beetles).

Imported from various parts of the world, probably in breeding pots, the flatworm is an invasive species that can significantly harm biodiversity and in particular earthworm populations.

Predominantly present in coastal areas in 2014, the species obama nungarathe most virulent is now spreading inexorably over the entire territory…

I usually don’t talk about what I don’t know, since since the beginning of this blog I’ve opted for an approach based mostly on concrete experience of things. (and by the way, I confirm my choice when I see that several bloggers, whom I will not name, who started more or less at the same time as me, have sold their sites to SEO agencies… who don’t have of course other goals than making money by riding the wave of natural gardening… but whose inexperience and incompetence are apparent with each newly published article).

But as for this famous platyhelminthe, the pressure is on!

So I’m going to bend my editorial line to address this troubling topic based not on my own experience (I’ve never seen a flatworm), but on reader testimonials and my research (particularly Professor Justine’s blog , a specialist in the field).

What is the flatworm?

Obama nungara, a highly invasive flatworm species
Obama nungara, a highly invasive flatworm species – Photo credit: Jean-Lou Justine​, Leigh Winsor, Delphine Gey, Pierre Gros, Jessica Thévenot

The land flatworm actually includes several species:

  • obama nungara is the most common species in France. Indeed, it is found in 72 departments, and it is mainly present on the entire Atlantic frontier. Native to Argentina for the individuals introduced to France, Obama nungara, is a flatworm about 5 cm long and brown in color (from light brown to almost black); it comes out at night and feeds mainly on earthworms and mollusks
  • Caenoplana variegata is native to Australia and mainly feeds on woodlice, centipedes and spiders. It is found in the south and in Brittany. It is elongated (5 to 12 cm long) and has a distinctive yellow stripe on its back
  • Parakontikia ventrolineata was probably introduced to France from southern England, but is also believed to have originated in Australia. It measures from 1 to 5 cm, with an almost black back but dotted with lighter lines. Particularly present in Brittany, it is also found in the south. He likes to hide in the holes of snails in strawberries…
  • Caenoplana coerulea also comes from Australia, but would have passed through space for the specimens present on French territory. Very elongated (5 to 10 cm), its back is black with a lighter stripe, while its belly is blue. It has been observed in the Loire-Atlantique, Charente-Maritime, Haute-Garonne and in the Pyrénées Orientales.
  • The bipalium , which groups several giant species (there are at least 3 in France) (20 to 40 cm long). They come from South Asia and have a hammer-shaped head.
  • Platydemus manokwari comes to us from New Guinea. In mainland France it is only present in one place, the greenhouses of the Jardin des Plantes in Caen… but it is spreading in the West Indies. It feeds on snails and earthworms

For more details on these different species, including photos and distribution maps on French territory, see here.

Why is flatworm problematic?

The most problematic species to date is Obama nungara (but the other species mentioned above should not necessarily be neglected).

Very discreet because of its brown color and its small size, and no doubt because it is not good (it seems that it tastes “horrible”… according to those who have tasted it?), Obama nungara n There are no natural predators in Europe …

It also reproduces very quickly!

And it becomes very invasive.

However, as we’ve seen, terrestrial platyhelminthes feed mainly on earthworms (but not only – other benthic populations are also endangered)…which they devour as soon as they encounter them!

Some have already noticed a sharp decline in earthworm populations in the soil of their gardens, in favor of this invader.

Let’s not forget that earthworms are essential to the life of the soil…

Stopping the invasion therefore seems a necessity.

But there is currently no solution, natural or chemical, approved.

And crushing the spotted individual wouldn’t make much sense (if you have a few in the house, they are probably already numerous in the ground…).

So what to do?

What to do if you discover a flatworm?

For now, the only approach envisaged is to map the invasion…mainly to try and measure its impact.

For this, our participation, as soon as we find a flatworm, is essential.

Professor Jean-Lou Justine, from ISYEB (Institute for Systematics, Evolution, Biodiversity) is responsible for this data collection.

It is therefore up to him that you must provide your data.

  1. take a picture
  2. possibly harvest the individual (without taking it with your fingers) and put it in a small airtight box
  3. contact Jean-Lou Justine. He will tell you how to do it…

For more details on the protocol to be observed and to contact Professor Justine, see here.

Additionally, here’s a video about the “invaders” (no, you won’t see David Vincent there…but it’s just as scary!):

Will we ever be able to stop this invasion? Probably not…

What will the long-term consequences be? The future will tell…




Photo credit in one of the articles: by Jean-Lou Justine​, Leigh Winsor, Delphine Gey, Pierre Gros, Jessica Thévenot — (2020). CC BY-SA 4.0, Link