If you’ve seen a long, slimy worm with a flat, shovel-shaped head slithering across your patio stones, you’re not alone. At first glance, it looks almost alien — nothing like the typical earthworms you’re used to seeing after rain.
So what is it?
Most likely, you’ve encountered a hammerhead flatworm.
What Is a Hammerhead Flatworm?
Hammerhead flatworms are a type of land planarian — a predatory flatworm known for its distinctive, spade- or hammer-shaped head.
They are:
- Long and ribbon-like
- Slimy and glossy
- Brown, tan, or yellowish in color
- Equipped with a wide, flattened head
That unusual head shape is what makes them so recognizable — and unsettling.
Where Do They Come From?
Hammerhead flatworms are native to parts of Southeast Asia but have spread to many other regions through the movement of soil and plants.
They’re often found in:
- Gardens
- Flower beds
- Patios and walkways
- Damp soil
They prefer moist environments and usually appear after heavy rain.
Are They Dangerous?
To humans, they are not directly dangerous. They do not bite or sting.
However:
- They secrete mild toxins to subdue prey
- Handling them with bare hands is not recommended
- Washing your hands after contact is important
The real concern isn’t human safety — it’s environmental impact.
Why Gardeners Should Pay Attention
Hammerhead flatworms are predators that feed on:
- Earthworms
- Slugs
- Other soil organisms
Because earthworms play a critical role in soil health, the presence of hammerhead flatworms can disrupt garden ecosystems.
In areas where they are invasive, they may negatively affect local soil balance.
Important: Don’t Cut Them in Half
If you try to kill one by cutting it, you may accidentally make things worse.
Hammerhead flatworms can regenerate. In some cases, pieces of the worm can grow into new individuals.
If removal is necessary, experts often recommend:
- Using gloves
- Placing the worm in salt or vinegar
- Disposing of it properly
Check local environmental guidelines in your area.
Why It Looks “Unnatural”
The flat, shovel-like head and smooth, glossy body give it an unusual appearance compared to common earthworms.
Its movement is also different — more like a gliding motion than the typical segmented contraction of an earthworm.
That combination makes it look almost prehistoric.
The Bottom Line
If you spot a long worm with a flat, shovel-shaped head on your patio, it’s most likely a hammerhead flatworm.
It may look alarming, but it’s not a threat to people. Still, because of its impact on soil ecosystems, it’s wise to handle it carefully and avoid spreading it.
Sometimes nature surprises us — and not everything strange is dangerous.
