This chart of teen sentiment shows why Facebook should be glad it bought Instagram

Facebook may be the most dominant social media networkin the world, but that's not the case among teens.

According to a recent survey by Piper Jaffray, Facebook-owned Instagram is considered the "most important" social media among teens, accounting for almost a third of the total responses (32%). Twitter came in at second at 24%, although it dropped 3 percentage points from last year.

The decline is more profound for Facebook, which only received 14% of the votes, down 9 percentage points from the previous year. That puts Facebook in the same class as Snapchat, which ranked fourth with 13% of the surveyed teens citing it as the most important social media network. This was the first year Snapchat was an option in the survey.

BI Intelligence says the rise of Instagram and Snapchat may be attributable to their strong image- and video-sharing features. Snapchat's ephemeral nature also makes it a preferred choice for a lot of teens who tend to be more self-conscious than other age groups.