Prince William, Kate share sweet photo of daughter, Princess Charlotte

The Duke and Duchess of Cambridge honored a cause near and dear to them in a sweet way.

In an Instagram post over the weekend, Prince William and Kate shared a photo of their daughter, Princess Charlotte holding a butterfly as part of the Big Butterfly Count initiative.

The initiative, which was launched by Butterfly Conservation, is a survey aimed at helping the conservation assess the health of the environment by having participants submit a record of butterflies spotted in the U.K. It was launched in 2010 and has become the world's biggest survey of butterflies.

This year’s Big Butterfly Count began last month and ended Aug. 8.

“@SaveButterflies are encouraging us all to count these incredible creatures because not only are they beautiful creatures to be around but they are also extremely important,” the Duke and Duchess of Cambridge wrote in the Instagram post. “Butterflies are vital parts of the ecosystem as both pollinators and components of the food chain.”

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In the Instagram photo, Charlotte, who is 6-years-old, is seen gently holding a butterfly outdoors. William and Kate also shared several close-up images of Peacock and Admiral butterflies as part of the initiative.