Small white spiders found in the United States or Canada are likely to be goldenrod crab spiders of the species Misumena vatia. These spiders grow up to 11 millimeters, with males much smaller than females, and appear pure white when not using camouflage.
Goldenrod crab spiders are known for their use of camouflage. Their bodies are normally devoid of pigment, which makes them appear pure white. When standing on a goldenrod flower, the spider can produce a temporary yellow or orange pigment to blend in with the flower. After the spider moves away from the flower, it can excrete the pigment and return to its normal white coloration.