Within Volasertib order 3 h the fresh weight of dead bees was only reduced by 2.3% in sunshine (from 103.5 ± 9.8 mg (mean ± SD) to 101.1 ± 9.9 mg, 8 bees, Ta = 22.8 °C, radiation = 790 W m−2), and by 0.9% in shade (from 99.7 ± 13.0 to 98.8 ± 12.9 mg, 8 bees, Ta = 18.5 °C, radiation = 180 W m−2).

Therefore, the dead bees’ heat capacity remained rather constant in our measuring periods. Relative humidity in shade was 47.2% in immediate vicinity to the bees and 39.1% about 1 m beside the water barrel (measured with 5 mm diameter miniature sensors, AHLBORN FHA646-R). Weight loss per bee equals an evaporative heat loss of 0.5 mW in sunshine and 0.2 mW in shade. A main disadvantage of dried carcasses is their strongly reduced heat capacity, which influences their reaction to convection. In insects (bees) with a weight smaller than 30–40 mg the cooling rate increases especially steep (Bishop and Armbruster, 1999). Drying bees in turbulent air at a temperature of 65 °C for

PCI-32765 supplier 26 h (until they reached a constant weight) reduced their weight from 96.4 ± 16.7 mg to 30.0 ± 5.3 mg (12 bees). This reduced their heat capacity by about 69.9% (from about 0.323 to 0.101 J °C−1, using a specific heat of 3.35 J °C−1 g−1 for biological tissues). This is much higher than the decrease in fresh carcasses within a measurement period of 3 h (2.3% in sunshine and 0.9% in shade, see above). Another disadvantage of dried bees

medroxyprogesterone is their reduced body surface area. Drying reduced the cross-sectional area by 25.6% (from 52.6 ± 3.2 to 39.1 ± 2.6 mm−2, 12 bees), mainly because of a strong shrinking and bending of the abdomen. This means a reduction of absorbed radiation of roughly 10.6 mW per bee (at 790 W m−2). In dried specimens we were not able to expand the abdomen to its original length. However, in our freshly killed bees we could do this. If one assumes a partly (50%) restoration of the dried specimens’ absorbing area, there remains a loss of about 5.3 mW per bee (at 790 W m−2). This is about 10 times the error caused by evaporative heat loss of fresh carcasses (see above). Hadley et al. (1991) demonstrated that even in a desert cicada which is able to exhibit considerable evaporative cooling at high ambient temperatures, evaporation causes just a small temperature depression (<0.4 °C) at ambient temperatures below 37.5 °C. When we integrate the evaporative heat loss of fresh carcasses in sunshine and shade into Fig. 6 by reducing the radiative heat gain (W m−2) accordingly (considering the honeybee body surface area, Woods et al., 2005), the resulting shift of the regression lines increases the Tth − Ta values at a given radiation by only about 0.1 °C. Therefore, we conclude that any evaporative temperature “error” in our dead bees is below ∼0.2 °C.