Fig. 7. Velocity vectors and contours of spanwise flow velocity at mid down- and upstroke. A wing–body computational model of a fruit fly (Ai) at mid downstroke, and (Bi) at mid upstroke. Velocity vectors at two cross sections at 50% and 60% of the wing length, (Aii) and (Aiii) at mid downstroke, and (Bii) and (Biii) at mid upstroke. A color map denotes the spanwise flow velocity; a negative magnitude of the spanwise velocity points to a flow from the wing base to the wing tip, and vice versa. L.E., leading edge; T.E., trailing edge.