Mechanosensory control of compensatory head roll during flight in the blowfly Calliphora erythrocephala Meig

In the blowflyCalliphora flying stationarily in a wind tunnel, compensatory head movements were elicited by rolling the fly about its longitudinal axis (Fig. 1). Responses were recorded on video tape, and evaluated by single frame analysis. Active head movements were observed in response to visual and mechanosensory stimuli (Fig. 2). They are not made or caused by the head's inertial momentum (Fig. 11). Gravity, used by walking flies to align their head with the vertical, does not seem to be perceived during flight (Figs. 3–6) but has a passive stabilizing effect upon the flight attitude (Fig. 7). A difference in aerodynamical load of the two wings elicits a transient head roll partly compensating a banked attitude (Figs. 4–6). The majority of campaniform sensilla at the wing base seems suitable to measure wing load. Steady roll motion elicits a steady compensatory head roll which does not vanish even after 8 min of rotation at constant angular velocity (Fig. 8). Roll motion is most efficient at high roll speeds (100‡/s<w