No, Instagram hasn't started sending people notifications when you screenshot their public photos
There's one problem: It's not true.
Instagram did start letting you know if people screenshot your Snapchat-style direct messages (those photo and video messages that vanish after you've seen them.)
But Instagram doesn't send notifications if you screenshot a normal photo. The confusion comes from people seeing notifications that someone has screenshotted their message, and assuming it was a photo.
It's all explained in Instagram's blog post from November 21 (emphasis is our own):
Swipe right into the camera to take a photo or video, then tap the arrow to send it privately. You can choose a group or create one in just a few taps - and you can also send to individual friends at the same time. Send anything you want, from inside jokes to your worst selfies. Unlike other messages in Direct, these photos and videos disappear from your friends' inboxes after they have seen them. And you'll see if they replayed it or took a screenshot.
Sure enough, people have been freaking out:
These aren't niche rumours - the three tweets above have well over 20,000 retweets between them. The problem comes from Instagram's vague notification. It doesn't explain what the screenshot was of, just that a screenshot was taken. Instagram did not immediately respond to a request for comment.