Princess Eugenie shares never-before-seen photo from Beatrice's wedding

Princess Eugenie marked World Bee Day with a photo of her sister Beatrice, whom she lovingly calls using the nickname "Bea."

The royal took to Instagram on Thursday to "celebrate nature's bada** little friend with their black and yellow stripes." But instead of sharing pictures of the insect, she posted a couple of snaps of her older sister.

The first is according to Harpers Bazaar, a never-before-seen photo taken from Princess Beatrice's wedding to Edoardo Mapelli Mozzi. It shows the couple smiling next to each other. The second is from a more casual setting and seemed to have been taken during an outdoor adventure. It shows the couple sporting rain jackets as they posed for a selfie in front of a waterfall.

Princess Eugenie shared the images to congratulate her sister on her upcoming bundle of joy. Beatrice is expecting her first child with Mozzi and the baby is due later this fall.

"But our furry little friends have to share today with my big sis Bea who's got a little one on the way," Eugenie captioned the photos as she added, "Beabea and Edo huge congratulations on your news - can't wait to meet the little one." She included the hashtags #worldbeeday and #savethebees.

News of Princess Beatrice's pregnancy came on Wednesday courtesy of Buckingham Palace. The announcement read, "Her Royal Highness Princess Beatrice and Mr Edoardo Mapelli Mozzi are very pleased to announce that they are expecting a baby in autumn of this year. The Queen has been informed and both families are delighted with the news."

The baby news comes nearly a year since the 32-year old married the 37-year-old Mozzi in July last year. They had an intimate ceremony held at the Royal Chapel of All Saints at Royal Lodge in Windsor Castle. Her parents the Duke and Duchess of York Prince Andrew and Sarah Ferguson as well as Queen Elizabeth II and the late Prince Philip were in attendance.

Princess Eugenie can probably impart some knowledge about child care with her sister Beatrice now that she is a mum. She and her husband Jack Brooksbank are parents to 3-month-old August Philip Hawke.