Four common species of bumblebees have been disappearing over the past 20 years. A new study estimates that these populations have declined as much as 96%. The disappearance of the bees is still a mystery, but some scientists think that the bees may have been infected by a fungus called Nosema bombi, which is an invasive fungus from Europe.

Bumblebees pollinate important crops, such as blueberries and tomatoes. They are more efficient pollinators than honeybees.

Read more about this study on National Geographic News.

Read about the honeybee mystery on National Geographic Kids.

Get the facts on honeybees in the Creature Feature.

Photograph by Bill Beatty, Visuals Unlimited