Probably mites...buy at miticide. They will probably not be a threat...but kill those suckers anyway!

Rather than guess what they might be, and toss around some unneeded pesticide, take several in a small clear jar to a garden center where someone may be able to help you.

Another good resource is your county's Extension Service office which you can locate with this map: http://nifa.usda.gov/partners-and-extension-map