Quarter inch holes in mounds around my yard

Sorry, no picture at the moment. I have noticed numerous small mounds, rather like large earthworm castings, with about a quarter inch diameter hole down the center. They are turning up all over my yard. Watching closely, I have been able to spot something coming up the hole nearly to the top, but so far they stop and do not come out, or even come up far enough to give me a good look at what I expect will be their head.

I am thinking ground hornets are a possibility, but with so many individual holes, let us just say I hope not.
Possibly a ground dwelling bee?

I have only spent about five minutes watching and waiting. Probably just need to pull up a chair and wait them out.

Pretty sure they are not ants, holes are huge for ants, and not enough activity - I would expect to see an ant going in or out in the time I watched, not just holding station below the mouth of the hole.

Any thoughts?

Ooh, that reminds me of the year the 13-year cicadas came out when I was a kid not far from New Jersey. In the early spring, there were all these holes the size of a pencil stab mark into the ground. And then some time later the world filled with enormous and rather interesting, but waaaaay too numerous big bugs.

In my area they would be crayfish! They like to burrow in the mud.

http://en.wikipedia.org/wiki/Periodical_cicadas

Although it doesn't actually say there's a brood expected to come out in New Jersey this year, but I think there are lots of smaller broods on different schedules.

Maybe you should stock up on chickens right quick! Would chickens eat these, and fatten up on them?

Here's another page
http://www.gardenersnet.com/atoz/cicada.htm

Cicadas are a possibility, and I do have chickens. Mm.

As our periodic guests, the Magicicada also come with a cult following: Cicada Killers
http://en.m.wikipedia.org/wiki/Sphecius_speciosus

Last year our yard was full of wasp burrows, they're quite large and I've pinned some specimens over 2" long!

Have you gone out at night and shined a flashlight quickly across the hole?