Trade-Off between Foraging Activity and Infestation by Nest Parasites in the Primitively Eusocial Bee Halictus scabiosae

Figure 6

Support for the hypothesis that the aspect of morning temperature (for definition see Methods) determines the foraging activity of Halictus scabiosae and partially also the impact of nest parasites at the $H$ . scabiosae nest over daytime. The abscissa gives the time of the day in hours and the ordinates show the probability of the match ($P_m$) with which the morning temperature conditions affect (a) the foraging activity rate in Halictus scabiosae, and (b) the ratio of the impact rates of parasites at Halictus scabiosae nests. The temperature conditions in the morning for the bees or parasites (for definition, see Methods) refer to the ambient temperature which was measured outside of the nest as well as to the temperature inside of the nest, which has been introduced into the model as a virtual parameter in the range from 12°C (blue violet) to 19°C (bright orange). The probability $P_m$ was calculated by chi-square tests for each time step of 30 minutes of the entire observation time. (c) explains the assessment of the probability $P_m\text{;}$$P_m>.05$ (chi-square test) signifies similarity, and $P_m>.05$ signifies contrast. $T_m$: morning aspect of temperature on the three successive experimental days (${\text{d}}_1,{\text{d}}_2,{\text{d}}_3$) defined for the initial hour of experiments; $A_{\text{out}}(k_1)$ and $A_{\text{out}}(k_2)$: the relations of outflyer activities in the observation intervals $k_1$ (9:30–10:00 h) and $k_2$ (13:30–14:00 h) on the three successive experimental days (${\text{d}}_1,{\text{d}}_2,{\text{d}}_3$) with the $P_m(k_1)$-values 0.122 and $P_m(k_2)<.001\text{.}$$T(k_2)$: the temperature relations in the early afternoon in the observation interval $k_2$ with $P_m<.001$; the examples refer to a virtual nest temperature of $T_{\text{nest}}={16}^{°}\text{C}$ (d) gives the probability $P_m$ by comparing the morning aspect of temperature on the days ${\text{d}}_1\text{–}{\text{d}}_3$ with the ambient temperature later in the day. The graph shows that the match is decreasing over the day with $P_m<.05$ for nest temperatures greater than ${15}^{°}$C.

(a)

(b)

(c)

(d)