Yep I've seen them before, I've had a 3 season room for about 6 years now and have seen them a few times out there.
I've lived in Bartlett since 1989 and have seen them on both properties i've owned here since I moved out this way.
I sent the pic to a landscaper buddy of mine to see if he can ID the little booger for us but I think its a spider mite. I treat the outside of the house each spring with several bug sprays and powders to keep the creepy crawlers out as much as possible. All in all it works good except for the dam box elders, those little ****s seem to only die off by spraying them with a soapy solution. At least the house is cleaned with the mixture I use..lol...
As soon as my buddy responds I post the findings and possible solution.
Dan