To detect motion, primates, birds and insects all use local detectors
to correlate signals sampled at one location in the image with those s
ampled after a delay at adjacent locations(1-10) These detectors can a
dapt to high image velocities by shortening the delay(11-13). To inves
tigate whether they use long delays for detecting low velocities, we c
ompared motion-sensitive neurons in ten species of fast-flying insects
, some of which encounter low velocities while hovering. Neurons of be
e-flies and hawkmoths, which hover, are tuned to lower temporal freque
ncies than those of butterflies and bumblebees, which do not. Tuning t
o low frequencies indicates longer delays and extends sensitivity to l
ower velocities, Hoverflies retain fast temporal tuning but use their
high spatial acuity for sensing low-velocity motion. Thus an unexpecte
dly wide range of spatio-temporal tuning matches motion detection to v
isual ecology.