Fruit flies 'watch the sky to stay on course'

Unbelievable it may appear, but a new study says that insects like fruit flies do watch the sky to stay on course.

"If you go out in a field, lie on your back and look up at the sky, that's pretty much what an insect sees. Insects have been looking up at this view forever," Michael Dickinson at University of Washington, who was part of the study.

For their study, researchers, led by Peter Weir at the California Institute of Technology, analysed the behaviour of Drosophila melanogaster, or fruit fly, in a specially designed "arena" atop a building.

Using adhesive, they attached the insects to a metal pin, which was then placed within a magnetic field that allowed the fruit flies to move and rotate naturally but held them in place. Digital cameras then tracked flight headings.

During the hour before and the hour after sunset, the headings of flies relative to the position of the arena were recorded for 12 minutes.

The arena was rotated 90 degrees every three minutes, and when natural light was not altered by optical filters some of the flies compensated for the rotations and maintained a consistent heading.
When the arena was covered with a circularly polarising filter, eliminating natural linear polarisation light patterns, the flies did not shift their heading significantly in response to arena rotations.

The findings revealed that fruit flies can coordinate eye and brain functions for rudimentary navigation using light polarisation patterns, say the researchers whose findings have been published in the 'Current Biology' journal.

The next step is to try to determine why the flies select a particular heading, say the researchers.