When you're bored, you might start playing with a ball or other objects. Such behavior is common in people. Other animals like it too—that's why a dog fetches a stick, or a cat bats at toys. Play is an enjoyable way to pass the time. A new study finds that it's not just mammals that like to play. Bumblebees（大黄蜂）do it too, making them the first insects known to play.
In the study, Hiruni Samadi Galpayage Dona, an insect expert, did an experiment using 200 untrained bumblebees to see if they might play. Of those, 45 would be marked with a number when they emerged as adults.
A pathway was set up from the bumblebees' nest to a feeding area. One side contained small wooden balls that rolled. The other side had the same number of balls, but they were stuck to the floor. Half balls on each side were colored balls. The rest were left unpainted.
For three hours a day over 18 days, Galpayage Dona found bumblebees weren't so interested in the side where the balls didn't move, but they explored the side areas and interacted with the balls. Once they managed to roll a ball, they strongly preferred that side. They returned, climbing on the balls and rolling them around. She also found bumblebees preferred certain colors of balls.
"There's something about the mobility that is more interesting for the bumblebees than just colored objects," Galpayage Dona says. In another experiment, she sometimes left the balls out overnight. "When I came in the next day, I would always find some bumblebees rolling the balls." As with mammals, the bumblebees who played the most were the younger ones. Their play tapered off as they got older.
The scientists say it's not clear why the bumblebees roll the balls or whether they enjoy it. But the experiment raises important questions about how the insects' minds work and whether they have feelings.