With a 0.4 mm coxa scale, nine CxHP8 activation flies had 0.152 mm more rigid rotation error after control subtraction

Can rigid rotation at the coxa account for endpoint movement in a connectome-mapped sensory reflex? We tested released CxHP8 activation data from nine male flies and nine genetic controls. A distance from three landmarks gives the exact minimum endpoint error over rotations that align the observed coxa axes, with free axial twist. The main panel had 1,421 trials with equal condition-code and fly weights. At 100–200 ms after onset, the activation-minus-control on-off error was 0.152 mm, with a 95% whole-fly bootstrap interval of 0.094 to 0.211 mm. Lengths use an assumed 0.4 mm coxa. Signed base-to-tarsus distance increased by 0.074 mm. The observed coxa length also fell by 0.0097 mm. Thus, the released coordinates changed beyond rigid coxa rotation, but the result does not separate true articulation from movement-dependent tracking error. A constructed example shows that axis error can raise the score without changing coxa length. The result does not identify active distal motor neurons. Planned time, code, repetition and scale checks kept a positive contrast. Independent arithmetic reproduced all 3,069 complete trial outcomes. The package has the geometry proof, code, derived coordinates, source records, all numeric results, figures and repeat instructions.

connectome · CxHP8 · proprioception · Drosophila · leg kinematics · rigid rotation · pose estimation · motor module · tracking error · structure and function