Navigating Beetles

How a beetle can use the stars to navigate its way across the vast deserts of  Africa

It might look small and insignificant but the  dung beetle has its sights set firmly on the stars.

The beetle is the first insect proven to use  the light of the Milky Way to help steer its course.

Also known as the scarab, the tiny creatures  feed on animal droppings, which they fashion into a ball and roll away to a safe  spot where it is less likely to be stolen.

Expert navigator: New research has found that scarabs - also known as dung beetles - find their way through their desert habitat by using the stars of the Milky Way as a reference
 New research has found that scarabs –  also known as dung beetles – find their way through their desert habitat by  using the stars of the Milky Way as a reference

Although their eyes are too weak to  distinguish individual constellations, scientists found they used the  glow of  the Milky Way to navigate in a straight line, ensuring they do  not circle back  to the dung-heap and potential competitors.

‘Even on clear, moonless nights, many dung  beetles still manage to orientate along straight paths,’ said Dr Marie Dacke  from Lund University in Sweden.

‘This led us to suspect that the beetles  exploit the starry sky for orientation – a feat that had, to our knowledge,  never before been demonstrated in an insect.’

Field experiments on a South African game  reserve showed that the beetles were able to roll their dung balls along  straight paths under starlit skies, but not in overcast conditions.

The lighter band of the Milky Way's edge: While unable to pick out constellations, the scarabs could detect the light arcing over their heads
The lighter band of the Milky Way’s edge: While unable  to pick out constellations, the scarabs could detect the light arcing over their  heads

For the tests, the beetles were fitted with  tiny cardboard caps to alter their field of vision.

They were placed in a circular arena  surrounded by a meter-high black cloth, making it impossible for them to see  landmarks.

With no moon, it took much less time for the  beetles to roll a dung ball from the center of the arena to the edge when they  were able to see the sky.

When they could not look up, the time taken  increased from 40 seconds to 124 as they wandered aimlessly around.

The experiment was repeated in a Johannesburg  planetarium, with similar results.

The beetles performed equally well under a  full sky of stars, and when only the glow of the Milky Way was  visible.

Most stars would be too dim for the beetles’ tiny compound eyes to see, said the researchers. While unable to pick out  constellations, the scarabs  could detect the light of the Milky Way arcing over  their heads.

‘This finding represents the first convincing  demonstration for the use of  the starry sky for orientation in insects and  provides the first  documented use of the Milky Way for orientation in the  animal kingdom,’  the researchers wrote in the journal Current  Biology.

Previously only birds, seals and humans were  known to navigate by the stars.

Dung beetles also use the sun and moon as  compass cues, said the scientists.

They added: ‘Although this is the first  description of an insect using the  Milky Way for their orientation, this  ability might turn out to be  widespread in the animal kingdom.’

Attribution: Damien Gayle, Mail Online