What you’re describing—a small tower or chimney of mud pellets with a hole in the center—is almost certainly made by a burrowing earthworm, often called a worm cast “chimney.”
🪱 Most Likely Culprit: Earthworms
- Earthworms push soil up from underground tunnels, creating mud “castings”.
- In wet or soft soil, these castings can pile up into a little tower (chimney) around the hole.
- The hole in the center is the entrance to the worm’s burrow.
🌱 Why It Appears Overnight
- Worms are most active at night, especially after rain or watering.
- They come near the surface, push out soil, and build these structures quickly.
👍 Good News: It’s Actually Beneficial
- Earthworms improve soil by:
- Aerating the ground
- Enhancing drainage
- Adding nutrients (their castings are natural fertilizer)
So while it may look strange, it’s actually a sign of healthy soil.
⚠️ When It Might Be Something Else
If the structure is:
- Hard, dry, and clay-like → could be ants or termites
- Much larger or irregular → possibly crayfish (in very wet areas)
But your description (4 inches tall, central hole, mud pellets) strongly points to earthworms.
💡 What to do?
You don’t need to remove it unless it bothers you visually—just flatten it and it’ll disappear naturally.
If you want, you can send a photo—I can confirm exactly which creature made it.
