Movements of the hinged filter flap of the metathoracic spiracle (Sp2), are coordinated with wing beat cycle. During upstroke of the wings and the correlated down stroke of the halteres the flap opens. During upstroke of the halteres the flap closes. The opening facilitates the outflow through the Sp2. The closing restricts the respiratory inflow to the mesothoracic spiracle (Sp1). Sequence recorded with 60 fps exposing with 130 Hz stroboscopic flashes interfering with the wing beat cycles. The moving frames are a interference due to the different recording frequency and the strobe flashes. Playback frame rate is reduced to slow motion of 7 fps. using NIH ImageJ software. Male from field 65 mg.