Dung beetle occurs in coastal dunes and marshes around the Mediterranean Basin. They are also known as scarab beetles that were sacred to the ancient Egyptians. These insects roll balls of dung across the earth just as the sun god Ra rolled across the sky. A team of scientists from South Africa and Sweden have recently published a study indicating that there was a grain of truth in this belief. They found that these beetles use celestial navigation to roll their balls of dung in a straight path. The beetles orient themselves with star clusters and the wide band of star light we know as the Milky Way. These beetles were astronomers.
Scarabaeus sacer is the most famous of the scarab beetles. To the Ancient Egyptians, S. sacer was a symbol of Khepri, the early morning manifestation of the sun god Ra, from an analogy between the beetle's behavior of rolling a ball of dung across the ground and Khepri's task of rolling the sun across the sky.
When the moon is absent from the night sky, stars remain as celestial visual cues. Nonetheless, only birds, seals, and humans had been known to use stars for orientation. African ball-rolling dung beetles exploit the sun, the moon, and the celestial polarization pattern to move along straight paths, away from the intense competition at the dung pile.
Even on clear moonless nights, many beetles still manage to orientate along straight paths. The new study shows that dung beetles transport their dung balls along straight paths under a starlit sky but lose this ability under overcast conditions. In a planetarium environment, the beetles orientate equally well when rolling under a full starlit sky as when only the Milky Way is present.
This is the first time celestial navigation has been seen in insects but the scientists believe it may be common. This has environmental implications because even moderate light pollution can completely wash out all but the brightest stars. When that happens the insects may not be able to see the way to go.
For example consider the moth. Moths frequently appear to circle artificial lights, although the reason for this behavior remains unknown. One hypothesis advanced to explain this behavior is that moths use a technique of celestial navigation called transverse orientation. By maintaining a constant angular relationship to a bright celestial light, such as the Moon, they can fly in a straight line. The moths confuse the light with the Moon and circle instead of going somewhere.
For further information see Beetle.
Scarab image via Wikipedia.