These mushrooms are native to British Columbia, although originally from the more northerly areas than Vancouver where we live. They are now reported to be all around the world and were probably spread as a side-effect of forest exports. This is a toxic mushroom, it was once used to prepare an insecticide and this is the origin of its name. When it emerges from the ground, around mid-autumn, the cap is small, round and almost completely white. Once above ground, the cap grows rapidly and the white covering breaks up into the scales seen here. These scales can wash off in the rain.
This picture is a crop of the original image, we originally had a vertical composition but now prefer this tighter, horizonal view.