Scientists unlock secrets of moths

PUBLISHED: 11:53 10 April 2008 | UPDATED: 13:08 06 May 2010

Rothamsted scientists have discovered that migratory moths use a compass mechanism

Rothamsted scientists have discovered that migratory moths use a compass mechanism

SCIENTISTS from Harpenden have discovered that migratory moths use sophisticated orientation behaviour to influence their flight direction while soaring through the sky at night. This breakthrough study by Rothamsted Research s Plant and Invertebrate Ecol

SCIENTISTS from Harpenden have discovered that migratory moths use sophisticated orientation behaviour to influence their flight direction while soaring through the sky at night.

This breakthrough study by Rothamsted Research's Plant and Invertebrate Ecology Department has quashed the theory that the insects are at the mercy of winds that propel them towards their destinations.

Evidence

While it isn't yet clear exactly how they do it, the findings offer the first hard evidence that nocturnally-migrating insects have a compass mechanism, similar to that found in migratory birds.

The scientists found that moths only migrate on nights when the wind directions are broadly favourable, blowing approximately towards the south.

They select their altitude to stay within the fastest winds, therefore maximising their speed.

James Chapman, one of the researchers, said the moths had the ability to compensate when the wind direction was substantially off target - something known as partial compensation for wind drift.

That ability has also been observed in insects such as butterflies and social bees that fly just a few feet above the ground during the day.

Using entomological radar, the researchers estimated that in August 2003 about 200 million Silver Y moths migrated southwards over the UK, travelling at more than 50kph over distances in excess of 300km per night.

Mr Chapman said: "There has been speculation for many years about whether insects that rely on the wind for their migrations can have any control over the direction in which they migrate.

"If they don't have any control, in many years the majority of the autumn population would get blown in unsuitable directions and die - the so-called 'Pied Piper effect'.

"Our studies demonstrate that the moths can influence their direction and speed of movement in a number of ways."

The scientists believe that understanding insect migrants' spatial dynamics will become progressively more important in global agriculture because of their pest status and the rising frequency of migration due to global warming.

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