Abstract: A one-way insect screen limits ingress of insects to an enclosed area, yet allows egress of insects from the enclosed area, by inclusion of a number of one-way passageways. The passageways are made by a number of flaps, moveable by insects making egress but not readily moveable by insects attempting to make ingress. Flaps of varying sizes are used for different sized insects. Alternatively, flaps that require relatively little force to open a small way, but more force to open further, permit egress of different sized insects while limiting ingress of such insects.