Insects, equipped with complex compound eyes, can maintain a constant heading in their travels, some of them for thousands of miles. New research demonstrates that fruit flies keep their bearings by using the polarization pattern of natural skylight, bolstering the belief that many, if not all, insects have that capability.
"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," said Michael Dickinson, a University of Washington biology professor. "Insects have been looking up at this view forever."
Dickinson is the senior author of a paper providing details on the findings, published Jan. 10 in the journal Current Biology. The lead author is Peter Weir, a doctoral student at the California Institute of Technology.
The researchers noted that insects such as monarch butterflies and locusts maintain a constant heading while migrating thousands of miles across continents, while bees and ants hunting for food successfully find their way hundreds of feet back to the nest without a problem. That has led scientists to believe that the animals must possess a compass of sorts.
To assess how insects orient themselves, Weir and Dickinson examined the behavior of Drosophila melanogaster, a species commonly referred to as a fruit fly, in outdoor lighting conditions in a specially designed "arena" atop a building tall enough to be higher than treetops and other visual landmarks.
The researchers used a light-cured glue to attach the insects to a metal pin, which was then placed within a magnetic field that allowed the flies to move and rotate naturally but held them in place. Digital cameras 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 op
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