Research on the visual behavior of insects has uncovered a number of cues t
hat are used for controlling and stabilizing flight and for extracting info
rmation about the structure of the environment. Flies monitor their egomoti
on and maintain a straight course by sensing the patterns of image motion t
hat are induced in the eyes. Bees flying through a tunnel maintain equidist
ance to the flanking walls by balancing the speeds of the images of the two
walls. This enables them to safely negotiate narrow passages or to fly bet
ween obstacles. The speed of flight in the tunnel is controlled by holding
constant the average image velocity as seen by the 2 eyes. This ensures tha
t the bee slows down to a safer speed when the passage narrows. Bees landin
g on a horizontal surface hold constant the image velocity of the surface a
s they approach it, thus automatically ensuring that flight speed is close
to 0 at touchdown. Flies and bees distinguish objects from backgrounds by s
ensing the relative motion between the images of the object and the backgro
und. Ranges of objects are gauged in terms of the speeds of motion of the i
mages of the objects. Foraging bees estimate the distance that they have tr
aveled to reach a food source by integrating the optic flow experienced en
route-they possess a visually driven odometer.