Stingless bees live in dense tropical forests with canopies that reach over 40 meters (130 feet) high. Lush as tropical forests seem to us, competition for resources is tough if you’re a bee. When they find new food, they keep going back. And they’ll bring friends. How do bees remember where they found that last tasty morsel in a vast three-dimensional world?
Honey bees use a “visual odometer”, which gauges how far they’ve traveled based on the flow of images across their visual fields. New research by a team from UCSD shows that the distantly related stingless bee does, too. By papering stripes on the inside of tubes, which contained feeders of unscented sugar water, the researchers were able toy with the stingless bees’ visual odometer. As the bees fly through the tubes, they see alternating black and white stripes. Seeing the stripes pass by, the bees learned exactly how far into the tube they had to fly to find sugar water. Once they were all trained up, the researchers altered the tubes and looked to see how the bees navigated. By varying stripe width (and therefore the number of stripes bees pass by on their way to food), they confirmed that stingless bees don’t count stripes. Rather, they rely on their visual odometer, which tracks how fast the world passes by to estimate how far they’ve flown. That visual odometer breaks down when the stripes run the length of the tube and their world looks…exactly the same. Making the tube narrower or wider messes the bees up in a whole new way: the bees perceive the stripes moving at a different rate, and they navigate accordingly- going either too far, or not far enough. Lastly, the researchers found that stingless bees use their visual odometer to measure distances in all three dimensions, not just laterally from the nest. A good thing for bees that live in the forest’s understory.
My lemonade’s only half done. Tell me more about these stingless bees!
Stingless bees don’t do the “waggle dance” like the honey bee. They have their own form of communication: they jostle, vibrate, and make noises to share information with the colony. Most of the information seems to be on the order of: “I found food! It’s super sweet! And close!” Not “go here for food.” For the purposes of guiding hive-mates, they leave scent trails that can last about 10 minutes and they lead expeditions back to new food sources. Stingless bees and honey bees are distantly related, though the stingless bee is much older, with the oldest known fossil dating back 80 million years.
A stingless bee can use visual odometry to estimate both height and distance. Eckles MA, Roubik DW, Nieh JC. The Journal of Experimental Biology, Sept 15, 2012. doi:10.1242/jeb.070540
Signals and cues in the recruitment behavior of stingless bees. Barth FG, Hrncir M, Jarau S. Journal of Comparative Physiology, 2008. DOI 10.1007/s00359-008-0321-7
Image credit: David Cappaert, available under CCL. Source: http://tolweb.org/Apinae