To discuss our Namibian Termites and African Termites in general, one first needs to understand that Termites can be roughly grouped into those species that nest within their food (those nasty ones who help you destroy and break-down any wooden structure), usually wood, and those that nest elsewhere and must leave their nest in order to forage for food. Of the latter type, nests may be arboreal or subterranean, centrally located or dispersed into small, connected units. Most termites shun the open air and travel to and from the foraging area by way of subterranean tunnels or covered galleries. Many species also cover the foraged material with sheet galleries before dining (Intro photo: Hypopharynx Pseudergates by Webstagram)
In the central Namib desert, the subterranean termite Psammotermes allocerus Silvestri (Isoptera: Rhinotermitidae) builds its nest structures nearly 30 em deep into the dry sand of the Kuiseb river. Gallery systems protect the insects against unfavourable climatic conditions and reduce body-water loss occurring in all humidities below 98% Rh. Furthermore, the social structure of a termite colony contributes essentially to a reduction of individual water loss in subsaturated atmospheres as well as to a more efficient water uptake. Water vapour uptake from the atmosphere is not possible and free liquid water cannot be used as a water resource because of the strong surface tension of the water droplets. However, with the aid of their hypopharynx pseudergates of Psammotermes allocerus are able to extract water from the capillary system of loamy sand. The role of “water-sacs” in connection with water uptake and storage is still unknown.
The Photo above: Psammotermes allocerus (by unknown)
Many termites do not build mounds that show above ground, but construct entirely subterranean nests, with tunnels to the surface. The best known of these is the African harvester termite, Hodotermes mossambicus, largely thanks to occasional subterranean encounters during the digging of trenches for construction (Coaton and Sheasby 1975; Hartwig 1963, 1965). Large passages connect these subterranean nest to each other, and smaller ones give the termites access to the surface where they dump excavated soil and forage for grass. Foraged grass is first placed into small, superficial chambers for later transport to the nests and consumption. None of the reports on subterranean gallery systems describes architectural details of the tunnels themselves, or how they are constructed.
Termite mounds comprise a significant part of the landscape in northwestern Namibia. The vegetation type in this area is mopane vegetation, a vegetation type unique to southern Africa. As a first timer visiting Namibia one should notice the fact that, almost all termite mounds coexisted with trees, of which 80% are Mopane trees (Colophospermum mopane). Also, according to multiple biological studies, it was determined that the rate at which trees withered was higher on the termite mounds than outside them, and few saplings, seedlings, or grasses grew on the mounds, indicating that termite mounds could cause trees to wither and suppress the growth of plants. However, even though termite mounds appeared to have a negative impact on vegetation, they could actually have positive effects on the growth of mopane vegetation. Moreover, local people use the soil of termite mounds as construction material, and this utilization may have an effect on vegetation change if they are removing the mounds that are inhospitable for the growth of plants. Consequently, both termite mounds and human activities should be taken into account as factors affecting mopane vegetation as a whole.
The Photo above: Mopane Tree (by Etosha National Park)
As we mentioned above, the savannas of Namibia are dotted with the spectacular mounds of the fungus-growing termites of the genus Macrotermes (Termitidae: Macrotermitinae). These mounds can reach several meters high and represent a colossal engineering project for the termites that build them. These little insects are working and building like there is no tomorrow. According to modern research, the mound is a respiratory device, built to capture wind energy to ventilate the subterranean nest. The need for ventilation is of the highest importance. A typical Macrotermes nest contains roughly a million workers and a substantially larger biomass of the fungi they cultivate. Collectively, these organisms consume oxygen at rates similar to that of large mammals.
By various estimates, a single Macrotermes colony is the metabolic equivalent of a goat or a cow. Macrotermes mounds are also external organs of homeostasis. The composition of the nest atmosphere is tightly regulated. Typically, oxygen concentrations in the nest are 2% lower than the surrounding air, carbon dioxide concentrations are commensurably higher, and nest humidities are very high. These conditions are maintained throughout the year and in the face of considerable variation of metabolic demand from the colony. Such stability can only come about if the termites can match ventilation rate with the colony’s respiration rate.
They do this by making the mound a “smart” structure, which means that it must also be a dynamic structure. The soil is continually eroded from the mound and is replaced by soil carried by termites out to the mound surface. Roughly a cubic meter of soil moves through the mound each year in this way. The mound’s architecture is therefore shaped by the relative rates and patterns of erosion from, and deposition to, the mound. For the mound to be an organ of homeostasis, these patterns of active soil movement must be coupled to the composition of the nest’s atmosphere. For example, excessive ventilation rates would produce patterns of soil transport that reduce the mound’s capture of wind energy. Insufficient ventilation would elicit soil transport patterns that enhance the capture of wind energy.
Photos above: Southern Africa Termite mounds (by unknown)
The termites are attracted by light from a lantern lamp causing them to fall in large swarms and are collected and put in a clean container. Van Huis (2003) reviewed various methods of termite collection around Africa. The most popular and easy way used in the tropics is to collect them during the evening hours, by placing a basin of water right under the light source. As light is reflected on the water, termites are attracted and trapped on the water surface.
In Benin, winged termites (Macrotermes falciger) are collected after the rain in a large pan containing water placed under an electric light. In the absence of grid-enabled light, lanterns are placed in large empty pans to trap the winged termites.