Fig. 12. Collection of flow visualization images selected to show the process of identification of critical points. Bifurcations in smoke streaklines are diagnostic of critical points. Blue arrows point to stagnation points either where a smoke stream hits the wings or head, or where the flow over the LEV touches down on the top surface of the wings, or on the body. Yellow arrows point to the free-slip critical point above the body. Red arrows point to smoke bifurcation at the saddle point in the wake caused by the shear layer between the downwash behind the attached LEV and the upwash of the LEV that was shed from the previous downstroke. (A–C) Flow over the wings at about half wing length. (D–F) Flow over the midline and interaction with the wake. (G–H) The free-slip critical point above the midline.