Hammerhead worm slithering around Hamilton will make your skin crawl

Native to Southeast Asia, it’s been spotted in southern Ontario gardens this year.

John Warren Reynolds, a research biologist at Oligochaetology Laboratory in Kitchener, said hammerhead flatworms have lived in North America for more than 100 years. The species was first spotted on this continent in wet semi-tropical and tropical areas of the southern United States and Mexico. It may have spread north of the border through nursery plants.

Reynolds said hammerhead worms haven’t been seen in large numbers yet in southern Ontario, but he’s aware of about a half-dozen sightings this year in St. Thomas, London, Hamilton and Newmarket. Reynolds said evidence suggests climate change is allowing the species to expand its range.

“Things are changing and warming up, so there’s probably more of them around,” Reynolds said. “You’re getting species, plant and animal, up here now that you didn’t get 50 years ago.”

Also known as broadhead planarian, these slimy creatures secrete a neurotoxin that can lead to a tingling sensation or a rash on exposed skin.

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• Dec 31, 1969
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• Dec 31, 1969
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Gardeners should avoid touching them by hand. Instead, use gloves or a shovel to manually remove them.

“They’re not going to kill you, but they may give you a little tingling feeling,” said Reynolds.

These slimy pests live on earthworms, slugs and snails.

“If they can’t find food, they are cannibalistic, so they’ll eat one another if there’s nothing else around for them to eat,” Reynolds added.

While some toads and frogs may eat them, they could continue to expand their range if left unchecked in southern Ontario.

“The trouble with invasive species coming in, they often come in without their natural predators,” Reynolds noted. “That’s not a big problem in Southeast Asia, where they’re from, because they have predators over there.”

If you think you can stop them by cutting them into pieces, think again.

“If you cut them into a dozen pieces you get a dozen new worms,” Reynolds cautioned.

Instead of cutting them up, place them in a sealed plastic bag and leave it out in the sun. The worms will die and you can throw the bag in the garbage.

“You want to get rid of them if you find them,” Reynolds said.

Reports and photos of hammerhead worms in Ontario have been posted to iNaturalist.ca, an invasive species reporting platform.

In addition to iNaturalist.ca, you can use the Early Detection and Distribution Mapping System (EDDMaps) app to report hammerhead worms.

Asian jumping worms

Reynolds also warms gardeners to watch out for Asian jumping worms, another invasive species present in Ontario, Quebec and New Brunswick.

They were first detected in Ontario in Essex County in 2014.

Reynolds said Asian jumping worms create an ecological, environmental and conservation issue in forests and urban landscapes by decimating the leaf litter layer.

“They don’t do anything beneficial in the soil,” said Reynolds. “In fact, they make the soil less useful. They make it almost like coffee grounds.”

By contrast, native earthworms that feed on organic material in soils mix their waste with the soil in a microbe-rich environment, creating tunnels that bring in oxygen, drain water and create room for plant roots.

“They don’t look like the worms we’re used to seeing,” Reynolds added. “These ones come in iridescent colours that reflect the light.”