Sundry notes on termites from Howse
(writing in progress)
I had before me a book by P E Howse (1970) Termites: a study in social behaviour (http://trove.nla.gov.au/work/21215794?selectedversion=NBD66593).
I have extracted the following points, which may be relevant my various other Posts about termites.
According to Hegh E (1922) Les Termites, Partie generale, Brussels, the queen of Odontotermes badius lays eggs at a rate of 4000 per day, which would result in 1460000 per year. And the queen of Macrotermes natalensis can produce 36000 eggs per day, amounting on average to one per two seconds and 13 million per year.
It is accepted that Macrotermes constructs galleries down to the water table, whereas Trinervitermes does not (pages 22-24). Ruelle seems to be a reference for this.
The African pennant-winged nightjar is something of a termitebird in its reliance on termite alates (presumably of Macrotermes). We should investigate this.
The mounds of Macrotermes bellicosus reach 30m wide and 6m high, and occur at densities of up to 2.9 per ha. Up to 450,000 bricks have been made from one mound. However, “Macrotermes bellicosus is quite variable in its habits throughout different parts of Africa. In many parts of north-western Africa nests are predominantly below ground level and only rarely are domes or towers found projecting above the ground. They generally have a diffuse internal structure,...with groups of fungus chambers well separated from one another.”
Page 26: “In building, Macrotermes workers tend to bring up clay particles from near and water table.”
The defensive substance of Nasutitermitines, e.g. Trinervitermes, is actually a hydrocarbon rather than a true organic material, i.e. it contains only carbon and hydrogen, not oxygen.
The species of Odontotermes at the base of the Himalayas, which builds shelters so superficially similar to the termitaria of N. triodiae in Australia, seems to be O. obesus.
Macrotermes may build shelters of similar shape to those of Nasutitermes triodiae:
I have mentioned in previous emails that Odontotermes (O. obesus, inter alia, I think) in India builds shelters superficially remarkably similar to some of the termitaria built by Nasutitermes triodiae in northern Australia.
Please bear in mind that the structures built vary greatly – indeed extremely – even within a single species of termite. This can be seen in both N. triodiae and various spp. of Macrotermes.
Now I suspect that even Macrotermes natalensis may be capable of building shelters quite (superficially) similar to those of N. triodiae.
The reason is that I read in Howse’s book, on pages 108-112, that “The Macrotermes natalensis nests in the Ivory Coast are heavily fluted, with prominently projecting ‘ribs’ on the outer wall of the mound...Differences exist among the nests of Macrotermes natalensis in different geographical regions. Whether this is because some aspects of the nest form are dictated by certain ecological conditions...The Uganda nests of M. natalensis have smooth walls without the projecting ribs and in correlation with this the air circulation system is on a different pattern...There are conflicting accounts of the structure of the East African nests and a wide and thorough survey would be of great value, but at least in some regions basal holes in the nest are consistently seen, and in others, for example in regions of Ethiopia, the mound is relatively chimney-shaped and open at the top. The nests [still referring to M. natalensis] in the region of Kinshasa have formed the subject of an excellent and detailed study by Father Ruelle. They appear in many ways to be intermediate between the Ivory Coast and Uganda types: the young mounds are more like the former and the old mounds more like the latter...Ruelle investigated the growth of termite mounds, which are constantly enlarging and changing in shape and form...There is still a great deal to be learned about the behaviour of this amazingly versatile insect, Macrotermes natalensis.”
Bottom line:
It seems possible that some of the shelters of Macrotermes natalensis, an extremely widespread species occurring as far south as the Kei River in the eastern Cape, are similar in superficial appearance to some of the shelters of Nasutitermes triodiae.
Explaining how the air conditioning works in Macrotermes natalensis: “These contain part of an air duct system, which begins near the top of the nest as six to twelve radial canals, the thickness of a man’s arm, pass into the top of the ribs and, as they descend, divide into smaller branches two to three cm in diameter. At about ground level they reunite to form ducts 10-15cm thick which open below the nursery area in the cellar region. The microclimatic measurements that Luescher took at various points in this system demonstrated the existence of an air circulation based on convection currents.”
In the conspecifics in Uganda: “The warm air rises into the attic, as before, but from here ducts lead the air upwards into large but shallow apical cavities that lie just below the surface of the mound. The air pressure resulting from the rising currents forces air through the porous wall. Pressure is therefore low at the base of the mound where, as a result, air enters through large ducts that communicate between the cellar and the outside air.”
In the case of the conspecifics in Kinshasa: “the attic connected with ascending galleries, and... the radial ducts connecting the hive with the peripheral vertical ducts were very numerous and were present at various levels down to ground level. The peripheral ducts united below this to give enormous conduits that opened into the cellar about 50cm below soil level...that convection currents do exist...was made evident by the current of warm humid air that issued when one of the pinnacles was decapitated...This flow is in an upward direction in the attic and, at least in the mornings, in a downward direction in the peripheral ducts leading to the cellar. The flow in the ducts, however, may reverse in direction during the day, possibly because of local heating effects.”
See photos below of concrete casts of the duct system in Macrotermes natalensis.
http://www.esf.edu/efb/turner/old%20site/termite/Termite%20images/ruelle%20cast.JPG
http://www.esf.edu/efb/turner/old%20site/termite/Termite%20images/filled%20michaelseni.jpg
I have wondered how Macrotermes transports water to the surface. Howse seems to answer this on page 103:
“Macrotermes bellicosus...secreting watery saliva or watery crop contents on to the material of the nest.” This implies that the water is not ‘urinated’ or ‘defaecated’, but oozed out of the mouth either via regurgitation or via saliva.
Howse goes on to state: “Psammotermes, which lives in the dry desert sand of the Sahara, manages, rather astonishingly, to maintain a high humidity in its nest even though there is very little water content in the food it eats. Individual termites go down to the water table which may lie at a depth of up to 40 m – and bring up moist particles with which they ‘humidify’ the nest.”
Please note the implications for the grass circles in the pro-Namib, and the intercontinental comparison generally. There is no counterpart in Australia for Psammotermes, again hinting indirectly that the groundwater in Australia is unsuitable/unavailable? Now we have not one but two quite different types of termites known to fetch groundwater from depths of 40m or more in Africa, but we’ve yet to hear of any such termite in Australia.
(writing in progress)
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