A wriggling horror of a predatory worm filled with potent neurotoxins has been invading Ontario since as early as 2019, and this creepy-crawly, known as the wandering broadhead planarian (Bipalium adventitium) or hammerhead worm, is already being spotted all over southern Ontario in 2024.

These large carnivorous landworms native to Asia are considered invasive in North America, and wreak havoc on local ecosystems by preying on native earthworm species.

Easily identified by its namesake hammer-shaped head and signature dark red stripe, B. adventitium makes its home in places like gardens, using chemoreceptors to lock in on a chemical trail left by its victims.

After cornering an earthworm, the hammerhead worm will coil its body around its victim like a constrictor snake, then use a horrifying stabbing appendage called an everted pharynx to deliver a coup de grace.

Earthworms have no natural defence against this terrifying predation method, allowing hammerhead worms to stalk and kill earthworms in great numbers.

The wriggling critters may look harmless to larger animals, but they pack a potent neurotoxic punch that can pose dangers to humans and pets. The species present in Ontario is confirmed to contain tetrodotoxin, a neurotoxin found in some of the world's most deadly animals, like the pufferfish and blue-ringed octopus.

It is unknown if this toxicity evolved to deter predators, but the chemical can cause illness and even death if ingested by pets. Humans handling these worms may suffer skin irritation, and experts advise not to directly touch a hammerhead.

Rebecca Morton of Toronto-based Armour Pest Control told blogTO in 2022 that while these worms are still uncommon, "they have been spotted in gardens through the GTA over the past few years."

Sightings of these worms tend to spike in the damp spring and fall months, and these alien-like creatures have already been reported in numerous locations across southern Ontario this spring.

In early March, sightings of hammerhead worms were reported to observation platform iNaturalist from Newmarket and Hamilton.

Another hammerhead worm was reported in Hamilton on March 30, another in Woolwich on April 6, and, most recently, one of these creatures was photographed and reported in Toronto's Forest Hill Village neighbourhood on April 12.

Morton told blogTO, "if seen, it's critical to catch them without contacting bare skin and kill them with salt, vinegar, or neem oil, then dispose of them in a sealed container."