Place wall mounted ILTs down low to best catch day-flying insects like the housefly. Ceiling traps will catch flies; but it is the fly's nature to be below five feet high (even skimming the floor) when they are most responsive to ILTs. Generally speaking, the lower you place a trap, the more responsive flies will be to it.
Ceiling-hung ILTs are the trap of choice for night-fliers (such as stored product moths). They have a tendency to fly at higher heights in buildings. However, night-fliers exhibit a more intence, relentless response to light than day fliers (think bugs around a porchlight). Night fliers and day fliers can usually be handled with a well designed system consisting primarily of low, wall-mounted ILTs. See Strategic Installation for exceptions.