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These dents, divots, or holes recently appeared in the mulch, located in a covered area next to the house and deck. The holes look like inverted cones and are an inch or two in diameter at the widest part. There isn't any obvious insect activity. What are they, and are they cause for concern?

holes in mulch, an inch or two in diameter

LisaT
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These look like Ant Lion traps to me. Ant Lions are considered beneficial garden insects and are nothing to worry about.

Here's a blog post with a photo of an almost identical situation.

enter image description here

And another photo of traps in a more common, sandy location: enter image description here

That Idiot
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  • I believe you are correct That Idiot! I was shown these ant lions a few years back and was amazed. – stormy Sep 20 '17 at 10:09
  • Look like ant lion traps to me too. They tend to like sandy soil. If you watch an active trap, you'll often see them throwing sand out of the hole. – winwaed Sep 20 '17 at 14:14