Figure 2. The fly proboscis as a model system for directed reaching.
(A) A fly extending the proboscis towards food on the surface of an experimental chamber (sagittal view). (B) A male fly (left) courting a female (right), extending his proboscis towards the female’s posterior. (C) Points used for measurement of angles of the head (connected by the longer lines) and rostrum (shorter lines). Scale bar: 200 µm. (D) Measurement of haustellum angle. (E–G) Angle of head (E), rostrum (F) and haustellum (G) in males feeding or courting on a flat surface. n = 15 flies per condition. T-test (unpaired) *p<0.05, **p<0.01, ***p<0.001, N.S.: not significant. (H–I) Proboscis extension in response to a low (H) or high (I) sucrose droplet presented to the legs of a tethered fly. Scale bar: 500 µm. (J–L) n = 28 males each presented with sucrose once in low position, once in high. T-test (paired). (J) Angle of target from the fly at frame of first leg contact, when target placed in low or high positions, where 90° would be directly ventral to the eye. (K) Mean reach angle: angle from the posterior-anterior axis of the fly to the proboscis tip, averaged over proboscis extension bout. (L) Aim deviation: reach angle minus target angle. (M–O) Joint angles scored 200 ms after beginning of PE: head (M), rostrum (N), haustellum (O).