In the previous article, I described the Flir thermal camera technology. Unlike a regular thermal camera, which records only heat, the Flir camera uses heat and visible light. The software in the camera uses visible light to sketch in a picture and match it to the heat pattern. The resulting picture appears sharper. Last time we observed the heat from the flight muscles of individual bees. Now we observe the heat patterns from small colonies in observation hives.
For several consecutive cool summer mornings, the low temperature dropped near the upper 50’sºF (10ºC), which triggered the bees to begin cluster formation for warmth. Bees cluster at 57ºF (14ºC). That was the strategic time to look at the observation hive colonies, not in visible light, the usual way, but in their radiated heat signatures, where I worked almost in complete darkness. The thermal camera separated the hotter and cooler places in the hive and color-coded those regions.
My bee house, which holds 30 single-comb top-bar observation hives, is the perfect place for viewing the small colonies and the heat they produce. For example, the bee house has no windows, which can let in sunlight (heat) and could distort the thermal photographs. For reference, Figure 1 shows a typical observation hive in normal visible light with its opaque panels removed. Figure 2 shows a thermal photograph of one end of the bee house. An active observation colony is in the lower right hive. Its heat glows in rings through the opaque panel meant to keep the bees in the dark. That is, the panels blocked the visible light, but they were transparent to heat (because the panels were not insulated). The lamp above radiated considerable heat. Yellow was the hottest. The cool green room was at the ambient temperature of 63.6ºF (17.6ºC), a bit high. Typically the mornings had been cooler. The hive at the lower left with the opaque panels was empty, appearing all green, and was equal to the ambient temperature. (With no bees inside it, as a heat source, the hive was in thermal equilibrium with its microenvironment, the same color green.)
The two hives on the upper row of Figure 2 are also empty, except their glass panes are showing. In a low level of warmth (the reddish pink), heat from the lamp reflects in the glass of these two hives, a fact that will become important later on. As we truly explore these new thermal images with bees, it is critical to keep in mind this is color-coded heat, which the camera represents in different color scales. For a particular situation, I pick the best color scale to distinguish details and avoid distortions. The camera has nine color scales, and while I use all of them, I try to publish in only a couple of color scales to avoid confusion.
Figure 3 shows another observation hive radiating heat through its panel at a closer view. In this color scale, the central blue is warmer than the ring of pure red followed out to the cold violet background. The camera’s thermometer reported 71.5ºF (21.9ºC) on the outside blue surface of the panel. This morning right beside the hive, the ambient temperature was about 60ºF (15.6ºC). That approximate 10ºF (6.3ºC) temperature difference represented considerable heat loss, probably a larger difference in the winter. While not detrimental to the colony in the summer, it reminded me why …