"Worm tunnels" or fungal growth?

Strange growths on freshly sawn lumber turn out to be "fungal hyphae," not a tunnel made by worms or insects.June 4, 2012

Question
What kind of critter builds these tunnels? This is showing up in some week old poplar I sawed. This log had been laying off ground (on 4x4's) for approximately 3 months prior to sawing. We went through all this extreme heat. The bark was drying up and falling off. My plan was to air dry then kiln. I've never noticed powder post beetles leaving such a tunnel.

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Forum Responses
(Sawing and Drying Forum)
From Professor Gene Wengert, forum technical advisor:
I have seen fungal hyphae that look similar. Are you sure they are insects doing this?

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From the original questioner:
No visual of an insect in or near. Did see an insect out from there (long/narrow, hard shell, articulates in the middle, approximately 1/4-3/8" in length, 1/16-3/32" wide) but appeared a little too big for that. I do have some holes/tunnels/bores approximately 1/32" diameter, but not with this.

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From contributor R:
I had the same problem with some maple. The logs were sawed last summer and stored off the ground through the winter. I have never seen this in poplar or other woods. The customer liked the worm holes…?

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From Professor Gene Wengert, forum technical advisor:
Brush the little thingies off and then look for a worm hole. Determine the size (diameter). If it is indeed fungal, as I believe, you will not see a worm hole; only stain.

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From the original questioner:
Doc, you're correct. I've let it dry some and they're not coming back or reproducing. I thought this was an insect of some sort - never would have thought a fungi. Thanks for your wisdom.