I'm searching the very same question and from what I've seen and read online it appears they're mites of some sort or another, perhaps velvet mites or red clover mites or as I've named them the never-ending-hords-of-itty-bitty-red-dots. Anyhow most importantly everywhere I checked they've stated they don't bite and they pose no harm, unless you want to count bothersome if your situation is like mine as I've been sweeping them up 3 times a day by the dozens and I'm on day 3 now :( Someone somewhere in my searches said to use a miticide to control them, but I'm not familiar with the chemicals in that so I'd rather hold off and just keep sweeping as they're in my daughter's bedroom window. Anyhow good luck to you.