Almost always if you trap a female, the male will return and start the “courting” process to attract another female. I will remove the trap after removing/disposing the female but leave the nesting material in. According to sialis.org (and also my own experience) the male usually returns in a day or so to claim his box and sings for another female. When that happens and I am sure and will then set the trap in hopes of catching him. I have eliminated several males this season, just by watching, learning, and watching more. Yes, until you see a HOSP around and “claiming” a nest do you need to worry about installing the trap and only after he has a small amount of nesting material. I have also learned that if you wait too long and the nest is too high, the trap may not trip so I usually have to take out some material if it is too tall.