The visual systems of insects are exquisitely sensitive to motion. Over the
past 40 years or so, motion processing in insects has been studied and cha
racterised primarily through the optomotor response. This response, which i
s a turning response evoked by the apparent movement of the visual environm
ent, serves to stabilise the insect's orientation with respect to the envir
onment. Research over the past decade, however, is beginning to reveal the
existence of a variety of other behavioural responses in insects, that use
motion information in different ways. Here we review some of the recently c
haracterised behaviours, describe the inferred properties of the underlying
movement-detecting processes, and propose modified or new models to accoun
t for them. (C) 1999 Elsevier Science Ltd. All rights reserved.