When we moved into this house, there was a good population of Pholcidae (aka "Daddy long-legs") around - usually one per room or area, but under the house (my workshop area) there were at least a dozen. This was good, because they're pretty benign as spiders go (from a human point of view), but they keep the insect population down, and also prey on some other types of spiders, including redbacks and huntsman, which is definitely a good thing.
However, sometime relatively recently, they seem to have all vanished - even the ones under the house. We haven't done anything to actively get rid of them, except occasionally idly brushing away the obvious cobwebs here and there (but always leaving some behind). We don't use fly-spray or surface spray inside the house, in general.
So, where did they go ? How do we lure them back ?