Some Honeybees Fan to Keep Hives Cool

Certain bees in the hive act as fanners during the hottest part of the day.

Asian giant honeybees are masters of air conditioning, suggests a new study that finds some members of the hive even work as synchronized "fanners" to keep certain areas cooler than others.

The findings, published in the journal PLOS ONE, add to the growing body of evidence that very social species can, when acting in unison, become a "superorganism" that functions like a single animal. In this case, the bee ventilation system is comparable to a human or other mammal inhaling and exhaling.

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Lead author Gerald Kastberger and his colleagues from the University of Graz explain that Asian giant honeybees (Apis dorsata) build their nests "in the open," which makes them particularly prone to seasonal and day/night temperature changes, and has them facing "exposure to sun, wind and rain."

To help combat such problems, "the singular comb is covered on both sides with multilayers of worker bees, termed (the) 'bee curtain,'" the researchers added.

Kastberger, senior author Thomas Hoetzl and colleagues Dominique Waddoup and Frank Weihmann investigated colony cooling mechanisms with an infrared camera and a vibrometer that detected the movements of Asian giant honeybees in several nests located in Nepal.

The scientists found that certain bees in the curtain act as fanners during the hottest part of the day. The bees align their bodies to funnel air towards the cool nest regions. Because this involves multiple bees acting in unison, it is very similar to a mammal inhaling, the researchers say.

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They suspect that inner bees within the curtain stretch their limbs against the comb, thereby expanding the inner nest area where the queen and her brood often are. This expansion likely lowers the hive's internal pressure and draws in cool fresh air.

The ventilation cycle then probably completes when the curtain bees relax, causing warm, stale air to push out through the living curtain.

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The process is incredibly effective, enabling brood incubation within narrow temperature limits at a toasty, yet not burnt to a crisp, 95 degrees Fahrenheit.

The hive's temperature may also be affected when many bees simultaneously take a bathroom break.

As the researchers wrote, "Regularly, periodic mass flight activity dramatically affects the interior nest milieu, when a good part of colony members set off to defecate ...(which succeeds in) dumping excessive heat."

The bee superorganism is perhaps most impressive when someone decides to attack the nest.

In a flash, according to the scientists, the bee curtain opens up "in preparation for the mass release of flying guards."

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