Tis the season for the creepiest of crawlies, and with Halloween upon us and the ground littered with decaying leaves, it's a fitting time for a new wriggly addition to Toronto's ecological landscape.

Though this new arrival isn't necessarily a welcome one.

A new invasive species of earthworms, Asian pheretimoid worms, had only been documented in Canada once before back in 2014, but a wave of reports popped up across Southern Ontario this summer, including reports of the strange worms right here in Toronto.

These unusual jumbo-sized worms get the terrifying moniker "jumping worms" for their increased rate of movement compared to the earthworms we're more familiar with in this neck of the woods.

Invasive jumping worms are spreading in southern Ontario. In Windsor in 2014, they're now in Hamilton and Toronto.

Don't move soil (just like you don't move firewood).

New article by JW Reynolds & Mike McTavish: https://t.co/NWzkHjg1db

CBC story: https://t.co/oC8yamxCWG pic.twitter.com/OKBMNb74LH

— Jay Fitzsimmons (@JayFitzsy) October 28, 2021

Easily identifiable by their size — much plumper and longer than what you might be accustomed to finding in your garden — and a distinctive lighter-coloured band, these worms are also faster-moving than their smaller cousins, and earn their moniker by jumping when threatened.

Jumping worms may be the next big threat to northern forests. https://t.co/9EbE5GkKQI pic.twitter.com/2a3NUIvSkD

— The Nature Conservancy (@nature_org) October 31, 2016

Oh, and they also tend to cluster together in wriggling masses of as many as 100 worms per metre.

So just like a cockroach, finding one of these unwelcome critters is typically indicative of a much, much, bigger problem.

A study on the spread of the invasive species from John Warren Reynolds' Oligochaetology Laboratory in Kitchener and Michael Mctavish of the University of Toronto tracked the worms to gardens of private residences around the region, and even one of Toronto's semi-natural ravines.

And while it may seem like a sudden worm invasion based on a flurry of reports all from the last month, the report states that the level of infestation could be a sign that jumping worm populations were already well-established in the area.

So ignoring the glaringly obvious gross-out factor, why exactly are these super-sized worms such a bad thing?

They actually are a bit too good at their job, breaking down decaying leaf matter and enriching soil at a rate just too fast for our forest floors, making the earth too dry and grainy to support moisture and life.

It's suspected that these slimy serpentine interlopers hitchhike their way around the continent through the moving of soil and potted plants to new locations, spreading uncontrollably.

So if you see an unusually worm on the next rainy day, maybe give it a closer look, and check for that distinctive light band. It could be a wriggly intruder in your neighbourhood.