From Jim Logan
Scott Turner and Rupert Soar suggest that the circulation of air in termite nests is driven by wind blowing across the mounds rather than by convection currents within them (20 February, p 35). This may be so in the mounds they studied in Namibia – although it does not explain why the nest does not overheat and the termites suffocate on windless days – but it is not the case everywhere.
I have observed that the Macrotermes nests in Sudan and east Africa, and the Odontotermes nests in India use convection currents, as previously suggested by entomologist Martin Lüscher. You can tell by placing your hand over the top of a mound chimney: you should feel the warm, moist air coming out. It is possible to distinguish live termite nests from abandoned ones in this way.
A more dramatic demonstration is achieved by dusting talcum powder at the base of the mound. After about 30 seconds a plume of talc erupts from the top of the chimney.
Gatehouse of Fleet, Kirkcudbrightshire, UK
