Bee Culture By Jerry Bromenshenk December 21, 2015
Inspecting the Hive
Have you ever wished that you could check your bees without having to suit up, get the smoker going, and dismantle each hive for inspection? How about in the winter, when it’s too cold to inspect bees without chilling the cluster? Or maybe, you want to remove a bee colony from a wall or ceiling, but don’t know where it is or how big it is?
Television shows and movies portray spying on people behind walls. That’s a microwave technology, expensive, not readily available, and not yet adapted to looking at beehives. Infrared imaging, on the other hand, has been used to image bee colonies, although it is not true through the wall imaging.
Objects, including living organisms, emit energy as electromagnetic radiation (heat) and light. The full range of wavelengths, extending from gamma rays to long radio waves, is referred to as the electromagnetic spectrum. Colors that we see are only a very small part of the light spectrum. We can’t see the IR light from a television remote, and we feel infrared radiation from heat lamps and electric heaters. IR or thermal cameras image the surface heat emitted and reflected by objects.
First developed and used by the military in Korea, thermal cameras were used to find things like a tank covered by a camouflage net. The net makes the weapon invisible to most people, unless you are color blind like my father. Since his visual perception of the world was different, this masking failed to fool him; although he couldn’t see cherries on a tree except when the round shape was highlighted against the sky.
In the same way that heat from a tank can be easily imaged by an IR camera, the heat of the cluster of bees in a beehive that is radiated from the outside surface of a beehive can be imaged by an IR camera. It’s not truly through the wall imaging, but if the cluster is reasonably strong, it’s heat signature can be readily seen and sized. Properly used, an IR camera will almost always detect a strong cluster, but it may miss a weak or small cluster, particularly if the cluster inside the hive is far from the hive surface at which the camera is aimed. Also, frames full of honey retain heat, so a full frame or two on the outside of the cluster may mask the cluster from that vantage point.
A colony cluster has a distinctive shape and heat gradient, with the hottest part in the center core. A queenless colony usually yields a diffuse heat pattern, since the bees aren’t clustering tightly, if there is little or no brood. Side views can be misleading, especially if there are full frames of honey next to the wall of the box. The best imaging position is from directly in front or behind a hive and down from the top, if there aren’t honey supers above the brood nest. Since honey retains heat and reflected sunlight masks emitted heat from inside the hive, the best time of day to use an IR camera is early morning, when night time ambient air temperatures are lowest and clustering tightest.
Why IR and Why Now?
We started testing IR cameras for hive inspections for the U.S. army about a decade ago. Our objective was to allow a soldier to quickly determine whether colonies used for surveillance and search purposes were adequately strong and healthy. The first camera that we used was a custom-built, research grade instrument, built by our colleagues at Montana State University at a cost of tens of thousands of dollars.
In 2011, we published our findings and tips for use. At the time, the only thing about IR cameras that was readily available to most beekeepers was the article itself. Some contractors were using hand-held IR cameras for energy audits, a few plumbers and electricians were using them, and law and fire departments had begun to purchase and use them. But the price was just too high to be cost effective for beekeepers.
I purchased my first, low-cost, thermal camera for...