i saw a post that suggested lights be left on, in the belief that it
will deter bats from returning....
you could not get enough intensity to acheive that!

bats do not hunt in the daylight, but they can and will fly, in the
light.....lights on in thier nesting area is not to their exact taste,
but it is NOT a deterrent.......

this is part folklore, part old wives tale.......

bats in the attic are not good and DOES need attention.

you must be SURE they are all out BEFORE you seal of the way they get
in and out...what seems like an impossibly small opening, is probably
the exact hole they use!

be careful, bats can CRAWL most secretly and fast!

if you have more than one known bat...hire a professional
exterminator...in the long wrong it is SO worth it!