Reading one of the books in our libray says that M taught that gheckos (what they call the little lizards found behind hanging pictures, curtains, towels) are to be killed: you gain 100 virtues as a reward if killed with one blow, less if with 2 blows, less if with 3.
I admit they're annoying, but there must be a minimum of 5 I see regularly in the house and others I hear - I startle them when opening a curtain or adjusting a picture and they scuttle away, and no-one likes cleaning up the small messes they make each day - but I was told they help keep mosquitos down, and my landlord's suggestion of poison made me imagine small bodies rotting in the heat in some hideyhole hard to get rid of them. Maybe I'm just too squeamish to attack them and gain the "100 virtues".