Heidi Klum's derriere-flashing thong sets Instagram on fire [Photo]

Phew! it's getting hot in here and we blame Heidi Klum for it. The age-defying former Victoria's Secret model has got the temperatures soaring with her recent bootylicious Instagram post.

The 44-year-old took to the social media platform to share a couple of sexy pictures with her derriere in the focus. The America's Got Talent judge shared a thong-clad selfie with her 13.9 million social media followers, giving them an eyeful of her curvy body.

With her back facing the mirror, the German-born is curled up on a flight of stairs in a pair of black lingerie matched with a black pair of stilettoes and her face half hidden behind her shoulder. Her tresses cover her almost bareback in the heavily-filtered selfie picture.

Heidi looked like she was on a selfie spree when she shared a slew of pictures on her Instagram account before ending her night with the sizzling picture.

The pictures come just a week after Heidi returned from her romantic Mexican getaway with her new beau Tom Kaulitz.

Although age is just a number for the ex-VS model, Klum confessed that she does worry about growing old. Speaking to Maxim last month (while posing nude for the cover), she said, "My nose would grow like Pinocchio's if I said that I didn't feel some pressure about aging, as I am constantly asked about it."

"I'm in the public eye, and there's more scrutiny because of that. I can look at photos of when I was 24, and of course, I am going to look different now at 44 and having had four children — but, again, it's about being comfortable with yourself and what you see in the mirror. I'm not trying to hold on to the past or searching for a fountain of youth. We are all going to age, so I'm trying to embrace that, but not without a bit of a fight," she told the magazine.

Speaking to PeopleStyle, Klum shared that she works out to make sure she's in shape. "I run a little bit. I don't run like super fast or super far. But it's not really about how fast you do it. For me it's just like doing it, period."

The publication notes that Klum runs on the treadmill wearing ankle weights and does rear-focused "butt lifts" focusing on her inner thigh area. "It's always good to keep the muscles underneath working so that it is nice and toned. Toned is good," she added.