MATERIALS AND METHODS

This study was conducted at the Termite Laboratory, Faculty of Forestry, Bogor Agricultural University in a facility used for rearing C. curvignathus, during August, 2014. The temperature was measured in one of the termite nest rearing stations with a size of 150×100×100 cm as well as inside of the laboratory room where nest was located. The tools were small-sized thermocouples that can be placed into termite nests and a multimeter as the temperature reader. Microsoft Excel was used as a data processing software. Clock or timers were also used for the times observation. Temperature measurements were carried out for 3×24 h periods and the temperature recorded every hour. The first observations were conducted at 18.00 pm. The thermocouple was laid in the rearing chambers filled with termites.

Data analysis was based on a model sinusoidal equation developed by Bahtiar et al.^8,9 to fit the daily temperature cycle inside the termite nest and indoor temperature in the laboratory. The following model was chosen:

Where:

RESULTS AND DISCUSSION

The result of this study showed that the temperature inside of a nest on the first day ranged from 29.6-33.8°C, on second day 29.9-33.1°C and third day 29.4-33.2°C. While, the temperature outside of the nest (indoor temperature in the laboratory) provided the following ranges 27.5-33.2, 28.2-32.1 and 28.2-32.1°C, respectively (Table 1). Based on the temperature values in Table 1, changes inside the nest were lower than outside. In this case, temperatures in nest ranged from 29.4-33.8°C (changes 4.4°C). While, the temperature outside of the nest ranged from 27.5-32.2°C (changes 5.7°C). It means, termites can maintain the temperature inside the nest become more stable than its surrounding. Generally, temperature inside the nest was warmer than outside.

Table 1:	Temperature inside and outside of nest Coptotermes curvignathus

Lee and Wood¹⁰ said that diurnal temperature on the nest of termites varied daily but the temperature in the nest was higher than the soil or environment temperatures. Noirot¹¹ also stated that the temperature was higher outside the nest (environment) than the area where termites resided.

Fluctuations in the temperature inside termite nests tend to follow fluctuations of the outside temperature. Termite nest temperature observations on the first day showed that temperatures reached their lowest at 06:00 and reach their maximum at 14:00. On the second day temperatures reached their lowest at 07:00 and reached the maximum at 14:00. Meanwhile, on the third day temperatures reached their lowest at 05:00 and reached the maximum temperature at 14:00. The minimum temperature were generally reached in a minute before the sunrise while, the maximum temperature were reached 2 h after midday. Temperature fluctuations inside and outside the termite nests are shown in Fig. 1. These fluctuations are caused by solar radiation and earth-surface energy which can be analyzed by sinusoidal equation developed by Bahtiar et al.^8,9. The sinusoidal equation consider the effect of both sunrays radiation and earth surface energy on the daily cycles of air temperature and relative humidity.

Temperature differences in termite nests by day and hour can be caused by activity, the number of individuals in the colony, the heat generated by the food collected by the termites¹², termite metabolism¹¹ and the friction that occurs when the termites feed on the wood. In addition, Nandika et al.¹² stated that one way to maintain the termite nest temperature is thermoregulation so the temperatures in some parts of the nest may be different but still can be controlled by termites.

Based on the sinusoidal equation models^8,9, two equations were obtained that describe the average temperatures and temperature fluctuations inside and outside the nest. The equations were:

Based on these two models it can be seen that the average temperature of the termite nest is approximately 1.3°C higher than the temperature outside the nest, which can be seen from the value of the regression coefficient (a) in the equation, where the average temperature of the termite nest is 31.4°C, while the temperature outside the nest is 30.1°C.

Fig. 1(a-c):	Temperature fluctuations inside and outside of termites nest at (a) First day, (b) Second day and (c) Third day

Since, the a value is higher, It is stated that the temperature inside the termite nest is warmer than outside the termite nest. Woodrow and Grace¹³ showed that the temperature inside the galleries of dry wood termites Cryptotermes brevis is 24.33-37.04°C. Meanwhile, Krishna and Weesner¹⁴ reported that the optimum temperature for macrotermes termite nests is 29-32°C.

The fluctuations in temperature can be seen in the summed amplitude value of b and c. The amplitude value inside the nest is smaller than outside the nest. The mean amplitude value inside the nest was 0.98575 (from 1.49492+(-0.50917)) and the mean amplitude values outside nest was 1.80533 (from 1.82938+(-0.02397)). Temperature fluctuations measured and estimated inside and outside of the termite nests during 3×24 h observation periods are shown in Fig. 2. Termites are capable to maintain the temperature inside the nest so it become less fluctuating than the outside temperatures.

Fig. 2:	Temperature fluctuations (measured and estimated) inside and outside termite nests during 3×24 h observation periods

It showed the insulating capability of subterranean termites nest to ambient temperature.

CONCLUSION

Average temperature in the nest of Coptotermes curvignathus was 31.4°C (ranged between 29.4-33.8°C). This nest temperature was 1.3°C warmer than the temperature on the outside surface of the nest or in the laboratory. Nest termite temperatures fluctuate following its surrounding temperature but termites can maintain the temperature inside the nest, so it become warmer and less fluctuating than the surrounding.

SIGNIFICANT STATEMENTS

Coptotermes curvignathus can maintain the temperature inside its nest so it become warmer and less fluctuating than the surrounding.

ACKNOWLEDGMENTS

We wish to express their appreciation to Ministry of Research Technology and Higher Education of Indonesia and Bogor Agricultural University for the supports thus this study could be conducted. We also wish to thank Nadzirum Mubin for his help resolving this study.