| MadSci Network: Zoology |
Question: Given the total emptiness of the desert, I wonder how desert ants keep their bearings, how can they find their way back to their ant heap?
Raven & Johnson, in Biology, write: "It has recently been shown in a walking insect, the desert ant Cataglyphis, that the ocelli can read 'compass' information from the blue sky, using the pattern of polarized light in the sky as a compass cue; remarkably, the ants find their way back to their nest by using this cue".
In polarized light, all the light waves are vibrating in the same direction. Sunlight becomes polarized as it moves through the air. This is not affected by clouds, so the direction of polarization can be used for navigation even when the sun is not visible.
Ocelli are simple eyes which can distinguish light and darkness but which do not form an image. These are the only eyes which some invertebrates (animals without backbones) have; but other invertebrates, including many insects (such as ants) have ocelli and more complex eyes.