Here’s what triggers giant honeybees to do the wave

Giant honey bees send undulating waves through their open nests by flipping their abdomens up in coordination, a sight approaching predators seem to shy away from. A new study is revealing details about what triggers the behavior, known as glow.

That bright is stronger when bees are shown a dark object moving against a light background under bright ambient light, researchers report in September Journal of Experimental Biology. The experimental setup simulates animals such as hornets, one of the bees’ top predators, flying against bright skies, and shows which visual cues trigger the behavior, the researchers say.

The behavior “is intriguing, as it is possibly a way that one species of animal communicates with another to warn that they are capable of defending themselves,” says Kavitha Kannan, a neurobiologist at the University of Konstanz in Germany who was not involved in the study. to study.

Giant bees, including Apis dorsata, typically form open nests uncovered by other material in areas such as tree branches and window sills. In the new study, the researchers worked with two dorsal a. nests in the ceiling joists. Standing near the hives, behavioral ecologist Sajesh Vijayan moved circular pieces of cardboard of different sizes in shades of gray and black against a gray or black background. The bees glowed when a black object moved against the gray background, but not when the contrast was reversed.

It’s probably because the black-on-gray configuration “resembles a natural predator or natural condition,” says Sajesh, who goes by his given name, as is common in many parts of southern India. “These are open nesting colonies, so they are always exposed to a bright sky.”

The team observed little brightness during the dark twilight periods of dawn and dusk. Since the brightness is a response intended to be perceived by a predator or other unwelcome visitor, such as a bee from another colony, the researchers believe that other defensive behaviors could be at play during low-light conditions.

“We also think the glow is a specialized response toward hornets because it hasn’t really been reported in cases of birds attacking or flying past these colonies,” says Sajesh. Birds, on the other hand, “elicit a massive bite response.” That could be because approaching birds take up a relatively large spot in the bees’ field of vision, and at that point, the bees’ attitude may be “let’s not take any more chances, just sting,” says Sajesh.

In both hives, the glow disappeared completely when the bees were presented with the smallest objects, in this case a circle four centimeters in diameter. The result suggests that there is a minimum size threshold that triggers the waves.

The shimmering force did not decrease even when the bees were exposed to the artificial setting repeatedly, perhaps because it is advantageous to stay alert against predators such as hornets that make persistent attacks.

It is not yet known exactly how the bees perceive the objects in the study. “They could be seeing this object in motion, or they could just be responding to a reduction in their visual field,” says Sajesh.

The researchers plan to explore that question further. They are also designing experiments with LED screens to modify background colors and patterns and the shapes of objects to find out what kinds of shapes and even movement might be important to bees.