part of the decomposer community, and regularly found around worm composting sites and not a problem for the worms, but if you've got many indoors there's water problems someplace, wet insulation, leaky plumbing, etc, as they need moist living space

Bill

I had them in a previous house in the basement. The basement foundation was cracked and leaked small amounts of water. I would check around for a water problem if there are a lot indoors, just like squeeze says.