Termite
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? Termites |
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 Formosan subterranean
termites
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Families
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Mastotermitidae Kalotermitidae Termopsidae Hodotermitidae Rhinotermitidae Serritermitidae Termitidae |
A termite (also known as a white ant) is any member of the order Isoptera, a group of social insects that eat wood and other cellulose-rich vegetable matter. Most termite species are tropical or subtropical, but a few live in temperate regions. They are of great biological and economic interest.
Appearance and Morphology
Termites only superficially resemble ants; their "white ant" name is probably due to their similar size and social habits.
Termites have biting mouthparts and their soft bodies are small, rarely over 10 mm in length. They typically inhabit dark nests and tunnels, only venturing out when the winged alates emerge to leave their parent colony, when constructing shelter or, in the case of grass-eaters, when harvesting grass stems. The bodies of flying individuals are dark, while termites which remain in the nest are whitish with only their heads being lightly pigmented. The deciduous wings of termites are long and slender, in two pairs that are similarly sized and shaped. The name of the termites' order is derived from their having equal wings. The veins near the anterior margin of the wing are prominent with the rest only faintly marked. The wings are quickly shed after flight with a simple body flick when the swarming termites find a new nest site, pair up and dig in. The remnant of the wing is a distinct triangular scale.
Social Structure and Behaviour
As social insects, termites live in colonies that number from several hundred to several million individuals at maturity. They are a prime example of decentralised, self-organised systems using swarm intelligence and use this cooperation to exploit food sources and environments that could not be available to any single insect acting alone. A typical colony contains workers, soldiers, and reproductive individuals of both sexes, often containing several egg-laying queens.
Queen and King
At maturity, a primary queen can lay several thousand eggs a day. In physogastric species, the queen adds an extra set of ovaries with each moult, resulting in a greatly distended abdomen and increased fecundity. The queen is widely believed to be a primary source of pheromones useful in colony integration. The king remains only slightly bigger than an average termite and continues to mate with the queen.
Workers
Worker termites undertake the labours of foraging, food storage, brood rearing, nest maintenance and a proportion of the defence effort.
Soldiers
The soldier caste has anatomical and behavioural specializations, primarily against ant attack. Many have jaws so enlarged that they cannot feed themselves, but instead, like juveniles, are fed by workers. Some species have soldiers with the ability to exude noxious liquids through either a horn-like nozzle (nasus) or simple hole in the head ( fontanelle). Among the drywood termites, a soldier's enlarged (phragmotic) head can be used to block their narrow tunnels. Termites undergo incomplete metamorphosis, with their freshly hatched young taking the form of small termites that grow without significant morphological changes.
Hiding
Termites try to remain hidden, building tunnels in earth and wood. When they have to cross some impermeable material they build several feet long shelter tubes (from packed earth/feces).
Diet
Termites are generally grouped according to their feeding behaviour. Thus the commonly used general groupings are: Subterranean, Soil-feeding, Drywood, Dampwood and Grass eating. Of these, subterraneans and drywoods are primarily responsible damage to structures.
All termites eat cellulose in its various forms as plant fibre. Cellulose is a rich energy source (think of wood fires), but difficult to digest. Termites rely primarily upon symbiotic protozoa ( metamonads) and other microbes in their gut to digest the cellulose for them, absorbing the end products for their own use. The gut protozoa in turn rely on symbiotic bacteria embedded on their surfaces to produce some of the necessary digestive enzymes. This relationship is one of the finest examples of mutualism among animals. Most so called "higher termites", especially in the Family Termitidae can produce their own cellulase enzymes. However, they still retain a rich gut fauna with bacteria dominant.
Mounds
In some regions, notably arid tropical savannas, termites construct extremely large and elaborate mounds which house their colonies. These mounds can have very distinctive forms, such as those of the compass termite (Amitermes meridionalis & A. laurensis) which build tall wedge-shaped mounds with the long axis oriented approximately north-south. This orientation has been experimentally shown to ease the termites' thermoregulation workload. Some mounds can reach heights of 6 metres, but most species build mounds of less than two metres height. The structure of these mounds can be quite complex, providing thermal mass, solar collection, defence, atmospheric control, food storage, housing and even areas for agriculture where (in a few species) fungi are cultivated, being fed on collected food and carefully watered and maintained.
 Cathedral Mounds |
 Magnetic Mounds (nearly North-South Axis) |
Human interaction
Because of their wood-eating habits, termites sometimes do great damage to buildings and other wooden structures. Their habit of remaining concealed often results in their presence being undetected until the timbers are severely damaged and exhibit surface changes. Once termites have entered a building they do not limit themselves just to wood, also damaging paper, cloth, carpets, and other cellulosic materials.
Fighting termites
Precautions:
- Avoiding contact of wood with ground by using termite-resistant concrete, steel or masonry foundation with appropriate barriers. Even so, termites are able to bridge these with shelter tubes.
- Timber treatment
- Use of wood that is naturally resistant to termites
When termites have already penetrated a building, removing their means of access and destroying the colony with insecticides are usually effective means of stopping further damage. Another common method of treating termites in houses, used in Australia since the early 1930's, is topical application of arsenic trioxide powder. This slow-acting toxin is distributed by the workers before any symptoms occur and is capable of destroying the colony. More modern variations include triflumuron, fipronil and imidacloprid which are much less toxic to mammals. Slow-acting toxins are also delivered by a range of methods involving poisoned feed.
Ecology
Ecologically, termites are important in nutrient recycling, habitat creation, soil formation and quality and, particularly the winged reproductives, as food for countless predators. Globally termites are found roughly between 50 degrees North & South, with the greatest biomass in the tropics and the greatest diversity in tropical forests and Mediterranean shrublands. Termites are also considered to be a major source of atmospheric methane, one of the prime greenhouse gases. Termites have been common since the Cretaceous period.
Relationships and Evolutionary History
It has long been accepted that termites are closely related to cockroaches and mantids but new research has shed light on the details of termite evolution. There is now strong evidence suggesting termites are highly modified, social, wood-eating cockroaches. A study conducted by scientists has found that endosymbiotic bacteria from termites and a genus of cockroaches, Cryptocercus share the strongest phylogenetical similarities out of all other cockroaches. Both termites and Cryptocercus also share similar morphological and social features- most cockroaches do not show social characteristics, but Cryptocercus takes care of its young and exhibits other social behaviour. Additionally, the primitive termite Mastotermes darwiniensis exhibits numerous cockroach-like characteristics that are not shared with other termites.