How Honey Bees Stay Cool

[BeeMaster2]

Received the following from American Bee Journal.
Pretty interesting!

How Honey Bees Stay Cool

MEDFORD/SOMERVILLE, Mass. – Honey bees, especially the young, are highly sensitive to temperature and to protect developing bees, adults work together to maintain temperatures within a narrow range. Recently published research led by Philip T. Starks, a biologist at Tufts University's School of Arts and Sciences, is the first to show that worker bees dissipate excess heat within a hive in process similar to how humans and other mammals cool themselves through their blood vessels and skin.

I could not copy the picture but here is the note:
The top panel depicts the experimental hive. It shows that the high
heat area, colored red, grew within three minutes of cooling and
disappeared within nine minutes. The bottom panel shows how
the control panel gradually dissipated heat. There, heat persisted after
18 minutes of cooling. Credit: Rachael E. Bonoan, Tufts University

"This study shows how workers effectively dissipate the heat absorbed via heat-shielding, a mechanism used to thwart localized heat stressors," says Starks. The research is published in the June 10 edition of the journal Naturwissenschaften, which appeared on line April 24.

This discovery also supports the theoretical construct of the bee hive as a superorganism—an entity in which its many members carry out specialized and vital functions to keep the whole functioning as a unit.

Young bees develop within wax cells. For healthy development, the youngsters must be maintained between 32 degrees Celsius, or 89.6 degrees Fahrenheit, and 35 degrees Celsius, or 95 degrees Fahrenheit. In contrast, adults can withstand temperatures as high as 50 degrees Celsius, or 122 degrees Fahrenheit

Previous research has shown that workers bees, among other duties, control the thermostat essential to the hive's survival.

When temperatures dip, worker bees create heat by contracting their thoracic muscles, similar to shivering in mammals. To protect the vulnerable brood when it's hot, workers fan the comb, spread fluid to induce evaporative cooling, or – when the heat stress is localized - absorb heat by pressing themselves against the brood nest wall (a behavior known as heat-shielding).

But until the Tufts study, scientists did not know how the bees got rid of the heat after they had absorbed it.
Starks' team included doctoral student Rachael E. Bonoan, former undergraduate student Rhyan R. Goldman, and Peter Y. Wong, a research associate professor in the department of mechanical engineering in the School of Engineering at Tufts. Bonoan and Goldman collected data on seven active honeybee hives that were framed by clear Plexiglas walls.

Each colony numbered 1,000 to 2,500 adult bees. An eighth hive, empty of bees, was used as a control. Using a theater light, the researchers raised the internal temperature of all eight hives for 15 minutes. Temperature probes recorded internal temperature throughout the heating portion of the experiment.

As anticipated, the worker bees pressed their bodies against the heated surfaces near the brood. Like insect sponges, they absorbed the heat, which lowered temperatures. After 15 minutes, a time brief enough to prevent serious harm to the bees, the theater light was turned off.

Immediately following, heat movement within the hive and external hive temperatures were tracked via thermal imaging. Within 10 minutes of cooling, temperatures in the active hives were down to safe levels. Meanwhile, the control hive remained at 40 degrees Celsius. "Since the control hive did not have bees, the differences in temperature were likely caused by worker behavior," Starks says.

Using thermal imaging, the scientists observed that temperatures increased peripheral to the heated regions of the hive as the brood nest began to cool. The thermal images clearly showed that the bees had physically moved the absorbed heat in their bodies to previously cooler areas of the hive. "Moving heat from hot to cool areas is reminiscent of the bioheat transfer via the cardiovascular system of mammals," says Starks.


Jim

[BlueBee]

I wonder if that theater light bulb was an incandescent or a CFL :-D

Interesting but maybe an inefficient way to remove heat.  Most of us remove heat by evaporation of water.  Its large heat of vaporization removes a lot of heat.  However swamp cooling doesn't work real well when the air is very humid.  Still, I assumed some of the water the bees collect in the summer was really be used in that manner; to cool down the hives.  I guess I'm a bit skeptical of their conclusions, or maybe the thoroughness of the study.  Like what are the bees doing with all the water they are obviously collecting on hot days, if not cooling down the hive?

[Hops Brewster]

Probably halogen lights.  :)
I don't see in this study where humidity was mentioned.  Coming from the land of swamp coolers, I understand fully how evap cooling works.  It seems to me that the application of the heat lamp caused a near instant 'emergency' situation, and the subject bees used an emergency measure, shielding the young with their own bodies. When the emergency was ove, they went out to cool themselves.
Now, I would like to see what would happen if the heat was applied more gradually, with variable in humidity control, closer to natural conditions, and then slowly cooled, and with the subject bees given water.

[flyboy]

Funny thing. I was thinking about a solution for the heat issues in a hive. Has anyone devised a thermally activated (ie thermocouple) vent for hives? It would be fairly simple. Maybe another thread.....

[BlueBee]

Seems to me that the first step would be to keep the heat out to begin with!  What is the real source of the heat?  In most places it isn't the ambient air temp overheating the hive; unless you are unfortunate enough to live someplace that gets above 95F.  In most places it's going to be the radiant heat from the Sun (100watts/sqft) beating down on the hive that makes it too hot inside.  So I would insulate the hive and/or reflect the incident radiation as the first step in temperature control.  No I haven't built any thermally activated (ie thermistor) controls, but most of my hives are made of 38mm foam. 

[rookie2531]

Makes sense though, if you and your child were in a fire, you would hold them close to you and have the heat face you and be in between. As always good info, Jim

[BeeMaster2]

Thanks Rookie.
Isn't it amazing the they react the same way we would react to protect our children.
Bluebee,
I think the idea of the study was "how do the bees remove excessive heat" rather than how do we reduce the heat load of the hive. I agree with insulating the hive. Our problem down here is solar heat, not cold. I use metal telescoping covers with insulation on the inside to reduce the heat gain during the hottest part of the day.
Flyboy,
A friend of mine and the nearest beek to me designed and installed solar fans in the top of his hives. They only run when the sun is hitting the hives. He did it because the bees were not capping the honey and said one week after installing them the bees were capping beautifully.
Hops.
This was done in Mass. Not sure but umidity probably is not not a major factor. I think that shielding and direct contact is exactly what their reaction was to protect the brood.
Jim