By Erin Weeks
Watch a honey bee wiggle its abdomen on a flower or do the waggle dance in a hive, and you’ll have some idea of the variety of ways in which bees use their hind ends. Thanks to new research published in the Journal of Insect Science, the movement of the many-segmented bee butt is a little less mysterious.
In 2015, a team of researchers from Tsinghua University in Beijing used a high-speed camera to observe how honey bees curl their abdomens while in flight and under restraint. The work confirmed that bees can manipulate the shape of their abdomens (for instance, to improve stability while flying), but that they can only bend in one direction — down, toward the bee’s underside.
Now, in a follow-up paper, the same team has identified the mechanism behind that movement. Specialized membranes that connect a honey bee’s abdominal segments are thicker on the top of the abdomen than on the bottom, allowing curling in just one direction.
Honey bee abdomens contain up to nine overlapping segments, which taper and end with the bee’s stinger. Like little armored plates, the segments are made of tough chitin to protect the abdomen’s soft insides: the digestive tract, venom gland, and ovary/spermatheca (in queens and drones).
A thin, flexible layer of cells called the folded intersegmental membrane (FIM) is what connects the tough outer plates together, allowing each concentric segment not just to attach to its neighbor, but to slide into the next one. The authors call this movement “telescoping.”
“Our research on the ultrastructure of the FIM is of great significance to reveal the bending and flexing motion mechanism of the honey bee abdomen,” said Professor Shaoze Yan, one of the co-authors, in an interview. “During nectar feeding, a honey bee’s abdomen does high-frequency respiratory exercises and assists the suction behavior of mouthparts to improve the intake efficiency.”
In this experiment, the researchers looked at forager honey bees from a single hive on Tsinghua University’s campus. Using the same combination of high-speed videography and scanning electron microscopy as they did in 2015, the engineers recorded the abdominal wiggling of live honey bees and the internal shapes of dissected bee abdomens. The flying videos were shot at 500 frames per second, and the dissected abdomens were imaged in thin slices.
The microscopy showed that the membranes along the top of the honey bee’s abdomen are two times thicker than those on the bottom. This asymmetry allows the segments to lengthen on top and contract on the bottom, resulting in the unidirectional curling the researchers observed in the bees they filmed.
It’s a design that the paper’s authors suggest is ripe for exploration by more engineers, perhaps for use in aircraft design. The engineering world takes frequent cues from the natural world, and the honey bee is one of the planet’s most socially sophisticated animals. Humans might well have something to learn from its wiggling abdomen.
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