When Instagram users @mention a social contact and then tweet the photo, Instagram will automatically translate the user’s Instagram handle to his or her Twitter handle.
“If the @mentioned user has connected Instagram to Twitter, the user’s Instagram username will appear in the photo caption [and] the user’s Twitter username will appear in the tweet,” a blog post announced.
If the user hasn’t connected the two accounts, the “@” sign will be removed in the post to Twitter to reduce confusion for users on that site. If the name following the @mention is not an Instagram user name, the “@” sign will remain in the tweet.
Although Instagram works as a social network in its own right, many users rely on pointers to their photos from Twitter and Facebook.
Instagram at one point offered to “find your friends on Twitter,” but had to pull the service due to Twitter’s recent crackdowns on uses of its API.
Instagram is owned by Facebook.