Yukky, disgusting monster black flies keep appearing in the upstairs bedrooms. I've no idea where they're coming from, or what to do about them. DS keeps bringing me dead ones he finds on the window sills, saying 'dirty, dirty'. They certainly are. It's really freaking me out in an argh-I'm-38-weeks-pregnant-and-can't-cope-with-dirt kind of way. The house is clean, we have no pets, don't leave food out. Where, oh where, are they coming from??
Any advice, wise MNers?