WILDLIFE: Light shed on butterfly problem

A butterfly that uses the sun to navigate and tell the time ends up lost if kept in the dark for too long, scientists have shown.

Monarch butterflies, Danaus plexippus, use a sun compass when flying the 4,000-km journey from their autumn breeding grounds in the eastern United States south to Mexico.

Sandra Perez, of the department of evolutionary biology at Arizona University, tested the monarch's navigational system by comparing the movements of some naturally migrating butterflies with another group that had been kept in the dark.

Deprived of the sun, the second group's internal clock was shifted. When released, this caused them to misinterpret the position of the sun and set their navigational compass incorrectly.

The clock-shifted butterflies flew on a west-northwest course, 75 degrees away from the south-southwest direction taken by the first.