Temperature and water balance in Macrotermes colonies
The Macrotermes colony has long been an exemplar of social homeostasis among the termites. It achieved this iconic status largely through the pioneering work of the Swiss entomologist Martin Lüscher, who dubbed them "air-conditioned" termite nests in his famous 1960 article in Scientific American. In that paper, Lüscher pointed to a seeming trend to ever steadier temperatures in termite nests, culminating in the very steady temperatures he observed in nests of Macrotermes natalensis. He argued that this ever steadier temperature was the product of an evolutionary tendency toward homeostasis, supported by ever more elaborate structural addenda to the nest, such as the mound.
Ever since Martin Lüscher published his pioneering speculations, serious doubts have been advanced about the validity of his concept of an "air-conditioned" termite colony. Most of these doubts have focused on Lüscher's scheme of thermosiphon ventilation driven by waste heat from metabolism, outlined here. These doubts about mechanism have not undermined Lüscher's claim that the Macrotermes nest regulated its temperature with impressive precision, which still appears regularly in literature of termite biology and social homeostasis. Yet this claim, too,is proving doubtful.
This and subsequent pages outline the results of a study of temperature and moisture distributions in mounds and nests of Macrotermes michaelseni in the arid savanna of northern Namibia. These results undermine the prevailing idea that temperature is regulated in Macrotermes nests. They also point to a surprising aspect of social homeostasis in termite colonies: water balance.