What is it?

I was splitting wood on Saturday and found this interesting track when I opened a log. It's obviously caused by some sort of insect, but very precise and symmetrical. Looks "burned" on the side tracks, but not on the main tunnel. Reminds us of a bottle brush. Wonder what it is?

Update - December 18, 2010
A fellow baritone in the Peterborough Chamber Choir saw this posting and sent the picture to his son who knows about these things.  Here is the response:

Very cool!  That's a "gallery" likely produced by cerambicid beetles - aka wood borers.  Looks like a very successful mama with each of those cavities having housed a baby beetle that began as an egg, then a larva which carved out its own bedroom, finally pupating and exited the wood through the same hole that mama came in on.  The fact that all the pupal chambers are right next to where the eggs were laid means that they didn't eat much wood in the larval stage and instead probably relied on fungal mass that grew after mama inoculated the area with spores.