Termites and mounds

Nov 17, 2007 19:03 GMT  ·  By

During a safari in the African, Australian or South American savannas you will come across some strange constructions resembling the towers of a castle. Their architects and builders are the termites, insects of the Isoptera order. They are also called "white ants", but have nothing to do with the real ants (which are related to the wasps and bees); they are closer to...cockroaches. And termites are much older than the ants, being 200 million years old, when dinosaurs had not even appeared. Today, they are found everywhere in warm and subtropical regions, from 40o N to 40oS. In Europe, native species like Kalotermes flavicollis, living in the soil, found in France, Italy and Spain, hibernate. Archotermopsis wroughtoni reaches 3,000 m (10,000 ft) in Himalaya.

There are about 4,000 species, adapted to live in their dark nests, which harbor many parasites and commensals. The basis of their diet is made of cellulose, which they procure either from wood or dead grassy vegetation. They avoid open spaces, as their body is soft and termites are appreciated by many birds, mammals, reptiles, spiders and even...ants. There are mammal species whose diet is based on termites, like the anteaters and some armadillos from tropical America, the African aardvark and aardwolf (a species of hyena), and the African/Asian pangolins. Chimpanzees are famous for using tools for fishing termites. Even tigers eat termites and they are also hunted by birds, bats and lizards.

A termite colony is made of 1-1.5 million individuals. Inside a colony, like in ants, there are specialized castes, of soldiers and workers and a pair of queen and king, which found the colony. Inside the colony, individuals communicate using pheromones emitted by the tergal (back) glands.

Termite soldiers cannot feed by themselves and are all blind, but due to their highly developed olfactory sense and sensitivity for vibrations, they do their job very well. The Apicoterminae termites do not have soldiers, while in other species of termites there are small and large soldiers.

In some cases, the soldiers have hard, cylindrical, blunt heads with which they tap the entrances into the galleries when the nest is attacked. Other termite soldiers have huge mandibles, efficient against mammals (anteaters, armadillos, pangolins); in Capritermes the jaws can be asymmetrical.

Some South American species have soldiers which produce irritating sticky saliva. The salivary glands can make half of the body and in Pseudacanthotermes they form 90 % of the abdomen. In the case of Globitermes, the release of the liquid kills the soldiers, acting more like an alarm signal. Termites' saliva is generally antiseptic. In Nasutitermes, frontal glands produce a chemical which is spit precisely through a frontal cone.

The soldiers of the termite Termes panamensis snap their jaws at a speed that bypasses any other muscle-powered movement of any species: 70.4 m (220 ft) per second, even if over a distance of only 1.76 mm. When menaced by an intruder, the termite jams its mouthparts against each other employing four sets of muscles so large that they fill half of the volume inside the insect's head. The pent-up power is what permits it to snap its jaws past one another at such incredible speed in the intruder's face. The termite's jaws work like a saw, biting with incredible strength. This enables a termite to defend its nest in the restricted space of the burrows.

The workers are blind and live 125-150 days. They build and maintain the nest, take care of the queen, produce food and cultivate fungi and feed the other castes, eggs and larvae. In Zootermopsis, the workers also defend the colony, wrapping the enemy with boulders of fecal cement. Unlike ants, the workers and soldiers are sterile individuals of both sexes, not just females. Moreover, in some species, workers are more males than females. Workers can transform into soldiers when needed.

Workers process the food, the processed aliments being made of food plus saliva regurgitated from the goiter (stomodeal food) or coming from the rectum (proctodeal).

Pheromones emitted by the queen and the king inhibit the sexualization of the larvae, which will give soldiers and workers. The emergence of new sexually active individuals (which form new colonies) is controlled by the royal couple, the emergence of new soldiers by other castes (through pheromones).

At the beginning of the rainy season, sexually mature winged termites execute the nuptial flight. The workers make breaches in the nest's wall so that these individuals can go out. Termites are sexually mature at 11 months. After flight, sexuated termites cut off their wings. The female emits through the sternal glands pheromones which attract a male, and the two form a new colony into a cavity, the initial chamber, called copularium. At the beginning, they feed on their own fat reserves and eat wood. The first larvae are fed through regurgitation. After 3-4 stages, the workers feed the larvae and the royal couple.

The abdomen of the female atrophies due to the ovaries, and the queen gets 30 times bigger than a worker, most of it being formed by the egg-filled belly, which can reach 12 cm (5 inch) in length (while soldiers and workers are 1.5 cm long). She lays eggs continuously, about 30/minute, 40,000 per day, for 15 years; 20 million eggs for a lifetime. Being so large, she can move extremely slowly through abdominal contractions and with the feet. The small king that continues to mate with the queen for life (unlike in ants, where it dies after just one copulation and copulation is enough for the rest of the fertilizations) in the copularium. From time to time, an old queen is replaced by a young one. The eggs hatch in 20 days in the larvae chambers.

If the royal couple dies or a too large colony disperses, non-sexual workers transform into reproductive individuals.

Workers digest cellulose in food with the help of flagellates (Protozoans) or bacteria (60% of all termite species). In the process, huge amounts of methane, a greenhouse effect gas, are produced. But all studied termites can produce their own cellulase (cellulose breaking) enzymes and therefore can digest wood in the absence of their symbiotic microbes. Workers feed the other members of the colony with substances derived from the digestion of plant material.

Primitive termites eat wood; the evolved termites (Termitidae) cultivate fungi, cultivated on their own excrements, or eat wood, humus, dead leaves and vegetal matter. The fungi cultivated by termites (Termitomyces) degrades cellulose and are also eaten by humans. The primitive termites consume proctodeal food: a hungry termite touches with the antennae the abdomen of a worker, which eliminates through the rectum the proctodeal food.

Termitidae eat only stomodeal food: they ask for food by touching with the antennae the head and antennae of a worker.

The most primitive termites are Mastotermes in northwestern Australia and close islands. They make nests in dead wood and resemble cockroaches. Their sperm has 100 flagella, a record in the animal world.

Termites can make nests in the wood or build it in the trees, made of carton. But we associate termites with the spectacular mounds made in the clay savannas by Macroterminae termites.

Of all insects, and taking into consideration their size, of all animals, termites build the largest and most elaborate nests. In the tropical areas they form mounds which can be 7.5 m (25 ft) tall (in Africa and Australia) and have up to 12 m (40 ft) in diameter. As termites are on average 1 cm (0.4 inch) long, if humans did something similar, they would build a building 1,400 m (4,600 ft) tall (!). A mound can have a life of over 20 years.

Inside the mound there is a royal chamber for the queen (in Macrotermes belicosus, which makes cathedrals 3 m (10 ft) tall) they are 20x15 cm), the rest are alveolar rooms for larvae and fungi culture, all interconnected by galleries. The wall of a mound can be 40-50 cm (16-20 inch) thick. Below the ground, the termite mounds can have tens of levels. The mounds are made of sand or clay particles cemented by the termites' saliva, chewed wood /cellulose and feces. The resulting material is as hard as concrete: a barehanded man can do nothing against a termite mound. Some species have been known to create such durable walls that industrial machinery has been damaged in an attempt to break their tall mounds.

During the night, these termites (workers) go out to harvest plant matters up to about 50 m (166 ft) out of the nest.

The whole mound denotes an extraordinary precision and ingenuity. The mounds are not fix; some portions are destroyed and remodeled constantly by the workers. The mounds' form varies depending on the species, from castle towers to pagodas, huge mushrooms, stalagmites or dome (these types are preferred by predators, like lions or cheetahs, as observatories over the plain). Some species build a shield over the mound, protecting the roof of the mound against rainfall. But in fact most of the mound is underground. A termite mound can weigh hundreds of tons.

As termites avoid open spaces, they can dig underground galleries of hundreds of meters away from the mound, which have aeration tubes and form a complex and vast net around the mound. Termites can make their nests also in the trees, hanging from the branches.

The termites can maintain their fungi culture, keeping them wet, even during the most severe droughts. How? Termites are sensitive to drought. They dig galleries to the table water or underground springs, even 75 m (225 ft) deep (in the case of Macrotermes belicosus). Moreover, inside the termite mound, there is constantly a humidity of 90-95 % and a temperature varying between 29?C (84? F) to 31?C (88? F), necessary for both fungi and termites. The galleries form a perfect installation of conditioning air. The orientation north-south of the mounds also helps in thermoregulation. The column of hot air rising in the above ground mounds helps drive air circulation currents inside the subterranean network.

An analysis of the termite mounds can give a quick answer to the contents of deeper laying levels of soil and even rock.

Ancient African civilizations used the termite mounds to locate gold deposits. The unconventional "termite" technique is increasingly used by western companies looking for gold in Africa. Its advantages are obvious; there is less need for manpower and equipment, which has to be transported to remote areas, often without infrastructure, while the drilling work is left to the termites. Some termite mounds can be so rich in gold that dissolving them and panning the slurry provides a significant side income for poorer residents of tropical regions. In a prospected area, termite mounds are isolated, dug up and analyzed for gold.

Using this method, gold prospects have been found in Southern Africa and several countries in western Africa, like Mali and Niger. The mounds are everywhere in the terrain and sampling and analyzing is cheap, about US$ 20.00 per sample. Termite mounds have also been used to discover the Vila Manica copper deposit in Mozambique in 1973. Later, the biggest kimberlite (diamond) mine in the world - Jaweng in Botswana - was found by termite mound sampling. It all started when a geologist in the 1970s found a single fleck of a mineral named ilmenite on the ground's surface. Ilmenite is associated with a rock called kimberlite and kimberlite contains diamonds. The minerals were located deep at 40 m (120 ft).

Through their activity, termites enrich the soil in nitrogen. In the Austral Africa, mashatu trees (Xanthocercus zambesiaca) usually grow over a termite mound, the tree taking advantage of the soil fertilized by the termites. Termites also remove dry vegetation, decreasing the risk of natural fires.

Still, they can attack crops. Rhinotermitidae termites can attack crops (rubber trees, coconut palms, cotton and so on). Mictotermes make underground galleries, attacking the sugar cane while Ancistrotermes attack through underground galleries corn, sorghum, millet, sweet potato, manioc, eucalyptus and mango trees. In Sumatra, the coconut trees are attacked by Coptotermes curvignathus.

Termites can also attack the wood of the houses, inducing huge damages. 10% of the termite species do this. Sometimes, the owner does not even sense the presence of the termites till the house is down, as the wood attacked by termites looks untouched on the surface, even if completely hollow inside. Schedorhinotermes and Coptotermes destroy the wood objects.

Termite mounds impede agriculture and mechanization. In central Africa, Pseudacanthotermes spiniger makes nests 1.5 m (5 ft) tall with 1 m (3.3 ft) in diameter, which can be up to 100 per hectar.

Photo Gallery (5 Images)

Termite mound in northern Australia
Termite castesThe structure of a termite mound
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