I occasionally find these things in my house (Toronto, Ontario). I've never seen this insect before in my life. Most I've found were barely more than 1/8th of an inch long. I've seen 3 varieties at that size. Black and smooth, white and powdery/lumpy looking, and greyish powdery/lumpy looking.
The first time I ever saw the little white ones, I thought it was one of those quick little jumping spiders covered in drywall dust. I thought the thick hind legs were 2 stuck together.
The photos below show the biggest one I've ever found, at about half an inch long. The bigger ones are always greyish and lumpy/powdery. (Of course I've only ever found three of this size).
Sorry for the poor quality photos. What's fascinating about these guys is the large rear legs which give them a sort of mech-robot sort of look when they walk. They have 6 legs, and two short antennae.