Temperature inside termite nests, notably mounds, has long been debated. Even though a number of research studies have been conducted, there remains a general curiosity – usually among members of the public – as to a well-founded answer (actually plural, as it is species-specific). As this aspect is not part of the scope of the Termite Project in the Kruger National Park (KNP) in liaison with Technikon Pretoria (1994–1997) and University of Pretoria (1998–2001), I have restricted this pursuit to a quick literature review slightly directed by personal communications with other scientists. (Red labels indicate some of the species found in the KNP.)

The internal temperature of active nests of soil-dwelling Nasutitermes exitiosus in Australia was reported by Noirot (1970) to be 8–10ºC higher than ambience with lag (delay). Arboreal Coptotermes acinaciformis (Rhinotermitidae) nests were measured to be 33–38ºC interiorly. In forests of the Ivory Coast, temperature inside Cephalotermes rectangularis (Termitinae) nests is more constant because of thick capping, around 30ºC, and between 22 and 27ºC for Thoracotermes brevinotus (Termitinae). Nest temperature of Microcerotermes biroi (26–33ºC) and Nasutitermes princeps (28–35ºC) was recently studied by Leponce and co-workers (1995) in coconut plantations of New Guinea.

From West and Central Africa mound temperature of Macrotermes bellicosus was reported to be approximately 30ºC in the centre (several sources). Slight deviations from this were noted by Dr J.E. Ruelle for Macrotermes natalensis in southern Africa, especially under rainy conditions. Interior mound temperature for Macrotermes michaelseni is about 30ºC (Darlington 1991). Josens (1983) reported an interior mound temperature for Trinervitermes geminatus (Nasutitermitinae) in the Ivory Coast that fluctuates between 26 and 36ºC diurnally and seasonally, and outside the given range in the top section of the mound. For Tumulitermes pastinator (Nasutitermitinae) in Australia, mound temperature at the nursery oscillates between 13 and 26ºC over 24 h (Bristow & Holt 1987).

Body heat of organisms striving to thermoregulate such as ants, bees, solitary insects, (birds) and active reptiles converge around 35ºC, because biochemical reactions in watery medium progress optimally near that temperature (Holm, pers. comm.). However, such reactions usually take place in true thermoregulatory organisms like the endotherms (warm-blooded animals) (Holt, pers. comm.).

The ways in which termite species tend to thermoregulate are not discussed here. But strategies include termitarium architecture, diurnal and seasonal behaviour, heat sinks (water application), and metabolism of termites and/or fungi (if present).

References
BRISTOW, K.L. & HOLT, J.A. 1987. Can termites create local energy sinks to regulate mound temperature? Journal of Thermal Biology 12: 19–21.
DARLINGTON, J.P.E.C. 1991. Turnover in the populations within mature nests of the termite Macrotermes michaelseni in Kenya. Insectes Sociaux 38: 251–262.
JOSENS, G. 1983. The soil fauna of tropical savannas. III. The termites. In: Bourlière, F. (ed.). Ecosystems of the World 13: Tropical Savannas. Pp. 505–524. Elsevier, Amsterdam.
LEPONCE, M., ROISIN, Y. & PASTEELS, J.M. 1995. Environmental influences of the arboreal nesting termite community in New Guinean coconut plantations. Environmental Entomology 24: 1442–1452.
NOIROT, C. 1970. The nests of termites. In: Krishna, K. & Weesner, F.M. (eds). Biology of Termites, Vol. 2. Pp. 73–125. Academic Press, New York.

Personal Communications
E. HOLM, Professor and former Head: Department of Entomology, University of Pretoria, South Africa (currently Ekogilde CC, Hartbeespoort, South Africa).
J.A. HOLT, Principal Research Scientist, CSIRO Land and Water, Australia (currently Associate Professor, School of Tropical Biology, James Cook University, Australia).

Compiled by Victor Meyer

In dedication to Prof. Erik Holm for his inspiring television programme Insek-Gedrag – Menslik Betrag.