I found some (apparently now vacant) "mud tunnels" in a wall void behind some drywall, in an area where water damage had occurred "over a winter." (This is in Utah FWIW–apparently we have both termites and carpenter ants present). Any guesses? termites? Carpenter ants?
and more 
. Thanks!
Pest Control – Identifying Mud Tunnels from Termites or Carpenter Ants
termite
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Those are definitely termite tubes. Those are the exploratory tubes that termites make when they come out of the soil and are exposed to air and light. They build the tubes out of dirt and their feces to protect them when out of the ground. Definitely termite tunnels. These are common on the side of a house, or inside a crawl space going up foundation walls.
DIY is definitely an option - a MUCH cheaper option. It's really simply in terms of knowing what to do, the hard part is the digging and drilling, but it's worth it when you know how much you will save. Read this article on my site to learn how to do it yourself: http://www.domyownpestcontrol.com/how-to-perform-termite-treatment-a-87.html
Not termites! According to an NMSU Entomologist who examined my pictures, they are a type of Springtail.
Thanks for turning me on to this whole "local cooperative extension" thing, Wayne. What a great resource!
Best Answer
Termites, without a doubt. That's the way they eat wood. Also, only termites eat drywall paper, as your second picture shows happened.