Fig. 13. Modeling of elytra motion. (A–C) Abduction of the left elytron by 90° versus different azimuth of the rotation axis (AAA). The smaller the azimuth, the more the open elytron tends towards a negative attack angle. (D–F) Supination combined with abduction; (D) supination of two elytra without abduction; (E,F) supinatory compensation of the attack angle to zero in the abducted left elytron. Initial position of elytra in A–E is horizontal, and in F is bent downwards. Angular variables are indicated in the panels: azimuth , elevation , abduction , bend ß, supination . Isometric view in the body-fixed reference frame. Inset below each model, we show the trace of relative divergence in projection on elytron-fixed axes t and b (i.e. across the suture) upon initial abduction in the hypothetical range ±10°. The tracer moves to the left on opening. Trace in D is computed for parameters in Cetonia aurata.