What is this?

[beauregaardhooligan]

Very close LabRat, but I'll let you have it.
Same idea, but different bug.
Those are the tracks of the Emerald Ash Borer.
The Dutch Elm Disease was a fungus spread by a bug. I don't believe the EAB spreads a fungus, it just eats all the growth layer out from under the bark and the trees die. You can tell there is a big difference in the way the tracks run.
There are ash trees dieing in Ohio and other states also right now from these things. Many communities are having to take down huge numbers of trees in an effort to stop the spread, and it is illegal to cross some county lines with the firewood. A real disaster for a tree that was so widespread and instrumental in American history.
As a prize, LabRat, I've got a cube for you!
{I was gonna send you one anyway, but this seems appropriate.}
Send me a pm with an address and I'll UPS it to you.