Termite “Fairy Circles”, Namibrand, Namibia
A reader asks about the colony size of the sand termite, Psammotermes allocerus.
A study by Grube and Rudolph* found a typical size of 2000 to 4000 individuals in a single nest sphere. Colonies may have multiple connected nest spheres, therefore the total colony size could be much larger. Grube and Rudolph* focused on water. The central Namib desert is a dry region with less than 28 mm of percipitation per year and long dry spells. In addition to providing termites with food, feeding on roots of plants creates the fairy circles and increases the moisture content of the soil surrounding the nest by eliminating plant evapo-transpiration. The nests are built to a depth of 30 cm with a “carton-like” material.
Colony life is essential to their survival. Termite individuals kept in isolation rapidly lose water, even at 93 percent humidity. The termites do not live long as individuals. Sand termites cannot collect water from the air as do some desert insects. When given water droplets, their heads become stuck in the water as they are not strong enough to break the surface tension and remove their head. Sand termites were able to successfully drink tiny droplets from a fine mesh by wicking water into their oral cavity using hairs present in the mouth adapted for that purpose.
*Sabine Grube & Dieter Rudolph. 1995. Termites in arid environments: The waterbalance of Psammotermes allocerus. MITT. DTSCH.GES. ALLG. ANGEW.ENT. 10:665-668.
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