Does thermoregulation occur in the mounds of the harvester termite, Trinervitermes trinervoides (Sjostedt) (Isoptera: Termitidae)?

The aim of this study was to obtain a seasonal profile of the mound temperatures of a harvester termite, Trinervitermes trinervoides (Sjostedt), to ascertain whether the temperatures in different regions of the mound were constant across seasonal temperature fluctuations. Temperatures were measured in six mounds in the Melville Koppies Nature Reserve (Johannesburg, South Africa). Unlike most epigeous mound-building termites, their mounds were wholly restricted to the surface with no subterranean component. Brood and queen were found at the core of the mound at the soil interface. Core temperatures were constant on a monthly basis but fluctuated seasonally. They were kept within narrow limits of 20 degrees C in May (winter air temperatures of 16.80 +/- 3.82 degrees C) and at 30 degrees C in October (summer air temperatures of 21.4 +/- 5.61 degrees C). Mound architecture was found to be an important influence on core temperatures as the core temperatures in the uninhabited mounds were also kept relatively constant. Large mounds had higher core temperatures than medium mounds during every month except May, but the same pattern of a lowered core temperature during the winter months was also observed. The daily core temperature variation during each month was also less in the larger mounds. The mound structure achieved the equivalent buffering of air temperature as would have possibly occurred if the nest was 20 mm below the surface. The increase in core temperature from August throughout the summer months was attributed to the presence of alate larval instars within the nest. These T trinervoides colonies were unable to build subterranean nests due to the bedrock layer occurring close to the soil surface, but achieved constant core temperatures through the insulating properties of the mound.