Red mite or not?

I've tried searching and there is so much red mite stuff on here its needle in haystack but...how do you detect red mite?  Put paper into a crack or something I read once....?

Can't see a red mite item in sticky but maybe I just didn't see it....

Red mite info here, http://chat.allotment-garden.org/index.php?topic=5250.0

Underside of the perch is normally the first place to check.