The effect of nest moisture on daily temperature regime in the nests of Formica polyctena wood ants
Relations between nest moisture and daily temperature regime were studied. Two extreme situations were distinguished among the variable patterns of daily temperature regime found. The first one was characterized by increasing temperature during the day and decreasing temperature during the night and was typical for dry nests exposed to sun. The second one was characterized by a lower temperature during the day that increased rapidly during the night. This pattern occurred in moist shaded nests and was less frequent than the first one.¶Patterns of surface nest temperature, which closely correspond with thermal loss, differ between dry and wet nests as well. In dry nests, the temperature decreased during the night on the whole surface in a similar way. In moist nests, the top parts constantly had a high temperature. The average surface temperature during the night was significantly higher in moist than in dry nests, which implies a higher thermal loss in moist nests. Microbial respiration of nest material strongly correlated with nest moisture, which implies a higher microbial heat production in moist nests.¶The results indicated two mechanisms for the maintenance of internal nest temperature. The first one, used in dry nests, is based on a combination of ant metabolic heat production and the isolation properties of a dry nest. The second one, used in moist nests, is based on the metabolic heat production provided by both the ants and the microorganisms in the nest material. These two strategies differ in the pattern of daily temperature fluctuation.