"Fig. (A) Infrared thermogram of the bees on the central comb of a broodless
winter cluster (3.5 s after cage opening was started, FLIR ThermaCam SC2000).
Note the warm thorax (yellow and white spots) of the endothermic bees with
shivering thermogenesis. Two additional measurements in the same cluster
confirmed this finding (not shown). The arrow points to the queen.
Bees that visited the surface are visible at the lower left end of the cluster.
(B) Temperature profile along the line marked in A; arrows mark
the thoraces of endothermic bees hit by the line. (C) Infrared thermogram
of the bees on the flat side of an outer comb (same cluster as in A);
one (periphery) to four (centre) bee layers. Ambient temperature was 5.5°C 3 cm
beneath the cluster and 3.7°C 1m outside the open cluster cage."