23/10/2012 06:58 BST | Updated 23/10/2012 07:14 BST

Monarch Butterflies Photographed In Sierra Chincua Reserve, Mexico

Fluttering and clinging to trees in their millions, the spectacle of these Monarch butterflies is almost other worldly.

The images were taken on the Sierra Chincua reserve in Mexico which hosts up to a billion migrating butterflies each year.

The wintering Monarchs from North America, make the almost 2,500 mile journey to the warmer climes of Mexico between October and March each year.

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The butterflies cling to trees to catch the sun ahead of their flight

During this time the butterflies congregate thickly on trees to conserve heat, open their wings to catch the sun's warming rays and at dawn take flight in their millions and mate.

With a wing span of four inches, the Monarch butterfly is known for its lengthy migration and is the only butterfly species to make annual north-south migrations like many bird species do.

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The Monarch butterfly is the only butterfly species to make annual north-south migrations

The Monarch migrates from North America to Central Mexico and back again each year, but with just a two-month life span it takes four generations to complete the journey.

Photographer Joel Sartore said: "It was like being in an orange blizzard at times, it was a really wonderful life experience and one of the reasons I enjoy working as a photographer.

"It's a world class spectacle that's well worth seeing and and experience you'll never forget."