sorry - another red mite question!

sorry to mention the dreaded topic of red mite! - but is it definately visible at night if i look with a torch? are they out and about or do i still have to search high & low for them - if i do that tissue rubbing thing on the perch and there is no sign of blood, does that mean theres no mites or just not enough to show up yet?  thanks for your advice in advance!!  ive become rather paranoid about them (even having dreams! - or should i say nightmares!)