Strange burrows

[lamprima2]

I often see these mysterious burrows at the edges of the trail in San Elijo Lagoon Preserve (Encinitas, California).
I've never seen any creature getting in or out of them. The holes are from about 5 to 15 mm in diameter.
Can anyone suggest a host?

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[wollastoni]

Some wild bees can make this kind of holes in France...
I guess other insects too...

[livingplanet3]

I often see these mysterious burrows at the edges of the trail in San Elijo Lagoon Preserve (Encinitas, California).
I've never seen any creature getting in or out of them. The holes are from about 5 to 15 mm in diameter.
Can anyone suggest a host?

They look much like the exit holes of cicada nymphs -

https://bugoftheweek.com/blog/2013/1/17 ... -brood-xix

- but 5-15 mmm suggests they are something else.

[58chevy]

Could be burrows of Sphecius grandis (western cicada killer)

[lamprima2]

Thank you all. The suggestions look reasonable,
though, I've never seen cicadas or Sphecius
in our area. I could overlook these insects, of course.

[Kona]

Vole burrows

[lamprima2]

Vole burrows

Too small for voles

[Cabintom]

Millipedes? I recently brought home a couple of millipedes from the forest (my daughter seems interested in them) and was surprised to find they had dug burrows all through the terrarium.

[Panacanthus]

I would bet on livingplanet3’s suggestion. These look more like “one time use” exit holes than repeat entrance/exit burrows, and there are at least 65 species of cicada in CA, some of them quite small, such as Okanagana bella.

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[lamprima2]

I agree: they look like exit holes.
I'll try to ask park rangers, perhaps they saw these
insects emerging.

[Kona]

Not insects. Not invertebrates.

Voles

[livingplanet3]

I would bet on livingplanet3’s suggestion. These look more like “one time use” exit holes than repeat entrance/exit burrows, and there are at least 65 species of cicada in CA, some of them quite small, such as Okanagana bella...

Another genus of small cicadas found in CA is Platypedia -

https://bugguide.net/node/view/1398422

[adamcotton]

Not insects. Not invertebrates.

Voles

I am sure everyone would be very interested to hear why you believe the holes are made by voles.

Adam.