Belcarra Garden Club
BC, Canada


Invasive Species - Hammerhead Flatworms
by Les Bramley and Nora Boekhout


(iStock internet photos)

The hammerhead flatworm also known as an arrowhead flatworm or broadhead planarian, gets its name from the half-moon shape of its head. It is often only 2.5 centimeters (one inch) long, but some grow to 38 centimeters (15 inches). This worm is originally from Asia and Madagascar.  Apparently, there are five sub species of this worm (Bipalium species), and it has turned up in many countries in the world. It is thought to have been transported through exotic plants.

Unfortunately, it is being found in Canada, with reports of them being found in Montreal (2019) and Ontario. The USA has them in several states now.  It looks like they were first found in the USA in 1901, so it is not exactly a new problem.  As with all invasive species, however, they are a problem for our native species. This predatory land planarian is a voracious feeder of earthworms.  It also feeds on snails, slugs, insect larvae, and other hammerhead worms. 

Hammerhead flatworms use a neurotoxin called tetrodotoxin, known as “TTX”, to kill their prey.  This little guy is not safe to touch (be sure to use gloves), and if a dog eats one then it will be ill for at least a day.  Actually, these worms are not good to be ingested by any other creature!

Hammerhead flatworms are sensitive to light and prefer cool, dark, moist areas.  They do not like acidic soil. A suggested method of disposal is to use gloves, place them in a plastic bag, pour Citrus oil, salt or vinegar on them, seal the bag, and then leave them in the bag for 48 hours. Additionally, you could freeze the bag. A very important note is that you should NOT try to slice them up. If these worms are cut into segments, it does not kill them it just regenerates and produces more.

To report invasive species in British Columbia phone 1-877-952-7277

Let's hope we never see this worm in BC.


CNN Science

Hammerhead flatworm

How to get rid of Hammerhead flatworms

BC Invasives - Take Action and Report
(note: I did not find Flatworm information here... yet!)
Report - Invasive Species Council of British Columbia (


 Back to Belcarra Garden Club