I have sawdust in my current woodpile, so I was searching for other's experience and ran accross this site. After reading the thread, I just had to join and give my 2-cents. Look at the pic. These critters are not harmless. The sawdust is over an inch thick in places, all since spring! Okay, facts: wood is 99% hickory. Larvae are same as the two pictures in this thread. They are in all the smaller, unsplit pieces, but are mostly confined to the bark of large rounds. I am separating the small rounds , and splitting the large. Hope that works well enought to save most of the wood for winter. I grew up in the country, and this is the worse problem of this type I have ever seen.
There isn't a single piece of pine up here that doesn't have the same type of boring bug in it. They do like wet wood. Trees I cut in the winter were too dry for them in the spring. And I can hear them chewing almost constantly. I believe its a large black beetle. And as far as i can tell, they are completely harmless. They won't touch a pile of 2X4s that are next to the woodpile.