Journal of Comparative Physiology A

, Volume 169, Issue 4, pp 451–459

A visually evoked escape response of the housefly

  • Mats H. Holmqvist
  • Mandyam V. Srinivasan
Article

DOI: 10.1007/BF00197657

Cite this article as:
Holmqvist, M.H. & Srinivasan, M.V. J Comp Physiol A (1991) 169: 451. doi:10.1007/BF00197657

Summary

Flies (Musca domestica) avoid danger by initiating a rapid jump followed by flight. To identify the visual cues that trigger the escape response in the housefly, we measured the timing and probability of escapes when the fly was presented with a variety of visual stimuli created by moving targets toward it. Our results show that an escape response is triggered by an approaching dark disk, but not by a receding dark disk. On the other hand, a bright disk elicits escape only when it recedes. A disk with black and white rings is less effective at eliciting escape than is a dark solid disk of the same size. This indicates that the darkening contrast produced by an approaching stimulus is a more crucial parameter than expansion cues contained in the optical flow. Escape is also triggered by a horizontally moving dark edge, but not by a moving bright edge or by a grating. An examination of several visual parameters reveals that the darkening contrast, measured from the onset of stimulation to the start of escape is nearly constant for a variety of stimuli that trigger escape reliably. Thus darkening contrast, coupled with motion may be crucial in eliciting the visually evoked escape response. Other visual parameters such as time-to-contact or target angular velocity seem to be relatively unimportant to the timing of escapes.

Key words

FlyVisionEscape responseMotionGiant fiber pathway

Abbreviations

Ps

Probability of successful escape

rdisk

radius of disk target

rarena

radius of shielding arena

vdisk

linear velocity of disk target

vedge

linear velocity of edge

ddisk

angular velocity of disk target boundary

ωedge

angular velocity of edge

ωescape

target distance at escape

dstart

target distance before onset of target movement

hedge

height of the edge above fly

xstart

distance from corner of triangle to start position of edge (0 or 50 mm)

xescape

distance from corner of triangle to the position of the edge when the fly escapes

xcenter

distance from corner of triangle to point above the center of the pad

xtotal

distance from the corner of the triangle to the base (height of triangle = base of triangle)

Copyright information

© Springer-Verlag 1991

Authors and Affiliations

  • Mats H. Holmqvist
    • 1
  • Mandyam V. Srinivasan
    • 1
  1. 1.Centre for Visual Sciences, Research School of Biological SciencesAustralian National UniversityCanberraAustralia