I’ve never heard of a tenant being responsible for removing insects from a rental property and you have stated that these ants are behind the walls, I say that the landlady is responsible for having that looked after. I’d check into that.

Thankyou for all the useful information on this webpage. We’ve been fighting a ants infestation for over 3 years now , we’ve steamed , we’ve used rubbing alcohol which the rubbing alcohol is effective for a day or 2 but then there’s a fresh outbreak and our throats and lungs simply cannot handle the massive quantities of rubbing alcohol in the air. We’ve found them in everything the walls , the sockets, the curtains , electronics , dresser frames and drawers , picture frames and even in the spines of books! I have yet to find a safe treatment for reading books. Definitely going to try the DE but if baking soda is just as effective it would be a lot more cost effective. Double sided tape may be good on the walls.