Temperature and relative humidity inside the mound of

Transcription

1 Prec. ndian Acad. Sci. (bnlm. Sci.), Vol. 89, Number 2, April 198, pp (~) Printed in ndia. Temperature and relative humidity inside the mound of Odontotermes obesus (Rambur) (soptera : Termitidae) V B AGARWAL Pest Control (ndia) Private Limited, New Delhi 11 1, ndia MS received 18 April 1979 ; revised 29 October 1979 Abstract. No diurnal fluctuation in temperature and relative humidity inside the mound of Odontotermes obesus (Rambur) has been noticed and the fluctuations through the year were within a narrow range (4 C ; 4 %). Sudden fall in temperalure from the maximum in May to the minimum in June, July and August was probably due to emergence of alates in June. Keywords. cology ; temperature ; relative humidity emergence. 1. ntroduction Temperature and relative humidity are two important abiotic factors in biology of termites. Temperature records of termite mounds and nests are inadequate. Grasse and Noirot (1958), and Cheema et al (1962) casually recorded temperature inside nests and mounds of various termites. Holdaway and Gay (1948) in Nasutitermes exitiosus observed that the temperature was not constant within the mound and varied with the time of the day and the environmental temperature. Ruelle (1964), on the other hand, recorded almost a constant temperature inside the earthen mounds of Macrotermes natalensis in Africa. Greeves (1964) observed in termite colonies of Coptotermes acinaciformis and C. frenchi in living trees that these colonies showed, little diurnal fluctuations in temperature. n so far as the Odontotermes is concerned, Perch (196) observed that the fluctuations in temperature ins[re the mound of Odontotermes redemanni were less marked thanthe fluctuations of external temperature. He, however, did not study the diurnal and seasonal fluctuation. With regard to relative humidity within the mound Fyfe and Gay (1938) in N. exitiosus gave an excellent account. Liischer (1961) studied the relative humidity in five species of termites in Africa and Cheema et al (1962) in the mounds of O. obesus. These studies were, however, not carried out throughout the year. F, xeept these, no other account regarding relative humidity inside termite nests seems to exist in the literature. The fluctuations of temperature and relative humidity inside mounds of O. obesus were therefore studied. P. ~B)--1 91

2 92 V B Agarwal 2. Materials and techniques The mound (height 3.8 cm) selected for the study was situated at New Forest, Dehra Dun. nitially, the temperature and humidity measurements inside the mound were taken continuously for six days. No daily fluctuations of temperature and relative humidity were noticed during the period. t was, therefore, decided to measure temperature and relative humidity only for 24 hr once in a month for a year. Temperature inside mound was measured using a soil thermograph of two long flexible arms connected to automatic recorder. The thermograph was calibrated with a standard mercury thermometer. A period of 12 hr was allowed for the adjustment of the apparatus to the new environment after insertion of the sensitive rods inside the mound. Measurements of relative humidity inside the mound were taken thrice in the day (civil time) and the readings were plotted on a graph. For measurement of relative humidity, an Assman's Psychrometer fitted to a specially fabricated glass apparatus having a tube of 1.2 cm diameter, one end of which was blown into a cup shaped wide bulb (diameter 2.3 cm) was used. The fan fitted with the Assman's Psychrometer aspirated out the air of mound through the narrow tube of the glass apparatus which was inserted inside the mound and the aspirated air passed over the mercury bulbs of the Psychrometer. The relative humidity was determined by a reference to Assman's Psychrometer Standard graph. The recordings were also checked with a dry and wet bulb thermometer, the arrangement of which was similar to the one used by Fyfe and Gay (1938) in Australia. Temperature and relative humidity of atmosphere were measured by a thermohygrograph calibrated with a standard mercury thermometer for temperature and with Assman's Psyehrometer for relative humidity. 3. Results 3" 1. Temperature 3.1 a Daily fluctuations : Figures 1, 2, 3 and 4 give the daily fluctuations of temperature and relative humidity inside the mound in winter (February), summer (May) and Monson (June and July). t is evident that there was no daily fluctuations of temperature inside the mound as against wide fluctuations in the atmospheric temperatures. 3.1 b Seasonal fluctuations : Seasonal fluctuations of mound temperature and atmospheric temperature (maximum and minimum) are given in figure 5. The mound temperature was not influenced by the temperature of the atmosphere. 3" 2. Relative humidity Figure 6 depicts the seasonal variations in relative humidity of the mound and atmosphere (maximum and minimum). Almost constant relative humidity inside the mound was recorded during the 24 hr period in all the months of the

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7 Temperature and humidity inside O. obesus maund e,o ~.~Mctximum 97,.--Mound ~-'3.la ~ \ i,,..minimum 1... x J ~.--.~ * Jan Feb Mar Apt May Jun Jty Aug Sep Oct Nov Dec Months Figure 5 1 _ Maximum 8 i \! i "g 6 t- q JN \ \ % Jr* Jan Feb Mar Apr MayJun Jly Aug $ept Oct Nov Dec Months Figure 6 Figt~res 5 and 6. Seasonal fluctuations of temperature and relative humidity inside the mound of O. obesus. 5. Temperature. 6. Relative humidity. year. The seasonal fluctuations inside the mound were within a narrow range (92-96 ~). 4. Discussion The seasonal fluctuations in mound temperature were within a narrow ranges compared to wide fluctuations o f atmospheric temperature. Similar observations were atso recorded in O. microdentatus by Agarwal and Sen-Sarma (unpttbliflaed

8 98 V B Agarwal data). Maximum temperature inside the mound was recorded in May, when alates were also present. The mound temperature suddenly fell in June, July and August. n 1973, the swarming of alates took place on 17 June (Agarwal 1978). Therefore, the fall in temperature inside the mound in June was probably due to the emergence of alates which took place about three days before the temperature was recorded. Similar observations were also made by Holdaway and Gay 948) in N. exitiosus and Agarwal and Sen-Sarma (unpublished data) in O. microdentatus. However, Ruelle (1964) could not confirm this in M. natalensis. The almost constant temperature inside the mound disagrees with the wide fluctuations of temperature recorded by Holdaway and Gay (1943)in N. exitiosus. Our results, however conform with the observations of RueUe (1964) in M. natalensis and Agarwal and Sen-Sarma (unpublished data)in O. microdentatus. The constancy of temperature inside the mound suggests some sort of thermoregulatory mechanism operating to achieve this admirable phenomenon. The architecture of the mound along with other factors seems to play an important role in the thermoregulation of the mounds. The underground portions of the mounds of O. obesus are almost equal to the above ground portions and the mounds of O. microdentatus descend more than half inside the ground. Notwithstanding the architectural pattern, the role played by huge population of termites in raising the temperature of the mound above the ambient due to their metabolic activities also merits consideration. n this connection, the observations of Holdaway and Gay (1948) that in dead nest, the internal temperature fluctuates with that of surrounding soil, is noteworthy. Liischer (1951) however, believes that the fungus combs may generate heat as a result of fermentation process and assist in the maintenance of temperature inside the mound. The thermoregulatory mechanism thus, seems to be highly complex and all factors like architecture of the mound, fermentation process of fungus combs, metabolic activities of the termites play their role in a highly coordinated and synchronised manner in order to maintain temperature inside the mound. Acknowledgements Thanks axe due to Dr P K Sen-Sarma, Dehradun for his guidance. of the Forest Research nstitute, References Agarwal V B 1978 Swarming behaviour in nature and colony foundation under laboratory conditions in Odontotermes microdentatus, Roonwal and Sen-Sarma and Odontotermes obesus (Rambur) (soptera, Termitidae) ; J. Bombay Nat. Hist. Soc Cheema P S, Das S R, Dayal H M, Koshi T, Maheshwaxi K L, Nigam S S and Ranganathan S K 1962 Temperature and humidity in the fungus garden of the mound building termites Odontotermes obesus (Rambur) ; in Termites in the humid tropics. Prec. New Delhi Symposium p Fyfe R V and Gay F J 1938 The humidity of the atmosphere and the moisture conditions within mounds of utermes exitiosus Hill ; J. Coun. ScL nd. Res Grasso P P and Noirot C 1958 Construction architecture ehes les termites Champignonnigtes (Macrotermifinao) ; Prec. loth nt. Cong. nt. Montreal

9 Temperature and humidity inside O. obesus mound 99 Grooves T 1964 Temperature studies of texmit colonies in living trees ; Aust. Y. Zool Holdaway F G and Gay F J 1948 Temperature studies of the habitat of utermes exitiosus with special re, fete, rice to the temperature within the mound ; Aust. J. Scient. Res. Ser. B Lfischcr M 1951 Air-Conditioned nests ; Sci. Am Pctch J 196 The fungi of certain termite nests Termes redemmmi Wasm and Termes obscuriceps Warm. ; Ann. R. Bot. Gdns Rue, lie J 1964 L' architecture dunid de macrotermes natalensis et son functionn l, A Bouillon ; in tudes sur les Termites Africains Leopoldville Univ. Kinshasha p P.(B)--2