Okay, so it's not necessarily on the ceiling, but I love this French expression: "une araignée au plafond." Translated, "A spider on the ceiling," is like "bats in the belfry" in English....
A.k.a. the person is crazy.
I think I'd have gone nutso if we had not evicted all the spiders from our house when we moved in this past July. The house had been empty for seven long months, so they'd moved in with their suitcases, their children, and their cousins' children, etc.... It was a long battle to convince them this was now our place.
This dew-dropped web is on a fence outside near the back patio. I can live with it there. But please, no more spiders on my ceiling or I'll end up with spiders on my ceiling!