As you say Rallem, maybe they do live underground like ants on Earth,......prehaps in the many caves on Mars?
View the 'seven sisters' here

http://www.space.com/scienceastronomy/070402_mm_mars_caves.html

...and this monster of a hole, here

http://www.space.com/scienceastronomy/070605_mars_hole.html

I find them interesting, since the "holes" are vertical, they are unlikely to be Asteroid hits. Also they seem to have very smooth edges.
Was'nt there a F Herbert, Science Fiction story about the Sand Worms of Mars?

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"You will never find a real Human being - Even in a mirror." ....Mike Kremer.