||This article includes a list of references, but its sources remain unclear because it has insufficient inline citations. (May 2012)|
Temporal range: 228–0 Ma Late Triassic - Recent
|Formosan subterranean termite soldiers (red colored heads) and workers (pale colored heads).|
Termites are a group of eusocial insects that were classified at the taxonomic rank of order Isoptera (see taxonomy below), but are now classified either as the infraorder Isoptera, or as epifamiliy Termitoidae within the cockroach order Blattodea. While termites are commonly known, especially in Australia, as "white ants," they are not closely related to the ants.
Like ants, and some bees and wasps — all of which are placed in the separate order Hymenoptera — termites divide labor among castes, produce overlapping generations and take care of young collectively. Termites mostly feed on dead plant material, generally in the form of wood, leaf litter, soil, or animal dung, and about 10% of the estimated 4,000 species (about 3,106 taxonomically known) are economically significant as pests that can cause serious structural damage to buildings, crops or plantation forests. Termites are major detritivores, particularly in the subtropical and tropical regions, and their recycling of wood and other plant matter is of considerable ecological importance.
As eusocial insects, termites live in colonies that, at maturity, number from several hundred to several million individuals. Termites communicate during a variety of behavioral activities with signals. Colonies use decentralised, self-organised systems of activity guided by swarm intelligence which exploit food sources and environments unavailable to any single insect acting alone. A typical colony contains nymphs (semimature young), workers, soldiers, and reproductive individuals of both genders, sometimes containing several egg-laying queens.
- 1 Etymology
- 2 Taxonomy, evolution, and systematics
- 3 Social organization
- 4 Distribution
- 5 Life cycle and reproduction
- 6 Ecology
- 7 Nests
- 8 Human interaction
- 9 See also
- 10 References
- 11 Further reading
- 12 External links
The Infraorder name derived from words translated from the Greek language "iso" (equal) and "ptera" (winged), which refers to the forewings and hindwings being around the same size of one another. The name termite derives from Latin and Late Latin, from the word termes ("woodworm, white ant"), and altered by the influence of Latin terere ("to rub, wear, erode") from the earlier word tarmes. Termite nests were commonly known as terminarium. In early English, termites were known as wood ants or white ant. First known use of the word termite is from 1781.
Taxonomy, evolution, and systematics
Recent DNA analyses from 16S rRNA sequences has supported the hypothesis, originally based on morphology, that termites are most closely related to the wood-eating cockroaches (genus Cryptocercus), to which the singular and very primitive Mastotermes darwiniensis shows some telltale similarities. Most recently, this has led some authors to propose that termites be reclassified as a single family, Termitidae, within the order Blattodea, which contains cockroaches. However, some researchers advocate the less drastic measure of retaining the termites as Termitoidae, an epifamily within the cockroach order, which preserves the classification of termites at family level and below.
The oldest unambiguous termite fossils date to the early Cretaceous, although structures from the late Triassic have been interpreted as fossilized termite nests. Termites have been common since at least the Cretaceous period. Termites also eat bone and other parts of carcasses, and their traces have been found on dinosaur bones from the middle Jurassic in China.[non-primary source needed] Given the diversity of Cretaceous termites, it is likely that they had their origin at least sometime in the Jurassic. Weesner believes that Mastotermitidae termites may go back to the Permian and fossil wings have been discovered in the Permian of Kansas which have a close resemblance to wings of Mastotermes of the Mastotermitidae, which is the most primitive living termite. It is thought to be the descendant of genus Cryptocercus, the wood roach. This fossil is called Pycnoblattina. It folded its wings in a convex pattern between segments 1a and 2a. Mastotermes is the only living insect that does the same,. However, all of the Paleozoic and Triassic "termites" have subsequently been determined to be unrelated to termites and are excluded from the Isoptera.
It has long been accepted that termites are closely related to cockroaches and mantids, and they are classified in the same superorder (Dictyoptera), but new research has shed light on the details of termite evolution.[non-primary source needed] There is now strong evidence suggesting that termites are really highly modified, social, wood-eating cockroaches.[non-primary source needed] 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.[non-primary source needed] 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. The primitive giant northern termite (Mastotermes darwiniensis) exhibits numerous cockroach-like characteristics, such as laying its eggs in rafts and having anal lobes on the wings that are not shared with other termites. Cryptocercidae and Isoptera are united together into the clade Xylophagodea.
As of 2013, about 3,106 living and fossil termite species are recognized, classified in 12 families. These are arranged here in a phylogenetic sequence, from the most basal to the most advanced:
- †Cratomastotermitidae Engel, Grimaldi, & Krishna, 2009 (1 Early Cretaceous species)
Clade Euisoptera Engel, Grimaldi, & Krishna, 2009
- Hodotermitidae Desneux, 1904 (3 genera)
- †Termopsidae (1 extinct genus)
- Archotermopsidae Engel, Grimaldi, & Krishna, 2009 (3 genera)
Clade Icoisoptera Engel, 2013
- Kalotermitidae Froggatt (22 genera, 419 species)
Clade Neoisoptera Engel, Grimaldi, & Krishna, 2009
- Arcehorhinotermitidae Krishna & Grimaldi, 2003
- Stylotermitidae Holmgren, K & N, 1917
- Rhinotermitidae (14 genera, 343 species)
- Serritermitidae (2 genera and species)
- Termitidae (236 genera, 1958 species)
- Apicotermitinae Grassé & Noirot, 1954 (42 genera, 208 species)
- Foraminitermitinae Holmgren, 1912 (2 genera, 9 species)
- Macrotermitinae Kemner, 1934 (13 genera, 362 species)
- Nasutitermitinae Hare, 1937 (80 genera, 576 species)
- Sphaerotermitinae Engel & Krishna, 2004 (1 species)
- Syntermitinae Engel & Krishna, 2004 (13 genera, 99 species)
- Termitinae Latreille, 1802 (90 genera, 760 species)
At maturity, a primary queen has a great capacity to lay eggs. In some species, the mature queen has a greatly distended abdomen and may produce 20,000 to 30,000 eggs a day. The two mature ovaries may have some 2000 ovarioles each. The abdomen increases the queen's body length to several times more than before mating and reduces her ability to move freely, though attendant workers provide assistance. Queen produced pheromones have been found to regulate egg production in termites, and egg production per queen in a multiple queen colony is much smaller in comparison to a colony with a single queen.[non-primary source needed]
The king grows only slightly larger after initial mating and continues to mate with the queen for life (a termite queen can live up to 50 years). This is very different from ant colonies, in which a queen mates once with the male(s) and stores the gametes for life, as the male ants die shortly after mating. If a queen is absent, a termite king will produce pheromones which encourage the development of replacement termite queens.
The winged (or "alate") caste, also referred to as the primary reproductive caste, are generally the only termites with well-developed eyes, although workers of some harvesting species do have well-developed compound eyes, and, in other species, soldiers with eyes occasionally appear. Termites on the path to becoming alates going through incomplete metamorphosis form a subcaste in certain species of termites, functioning as workers "pseudergates" and also as potential supplementary reproductives, but this usually develops quickly when the colony is large in size and temperatures are low.[non-primary source needed] Supplementaries have the ability to replace a dead primary reproductive and, at least in some species, several are recruited once a primary queen is lost. Supplementary reproductives developed from nymphs are called secondary reproductives.
In some species like eastern subterranean termite, reproductives can also develop from non-nymphs. These are called "tertiary reproductives". In areas with a distinct dry season, the alates leave the nest in large swarms after the first soaking rain of the rainy season. In other regions, flights may occur throughout the year, or more commonly, in the spring and autumn. Termites are relatively poor fliers and are readily blown downwind in wind speeds of less than 2 km/h, shedding their wings soon after landing at an acceptable site, where they mate and attempt to form a nest in damp timber or earth.
Worker termites undertake the labors of foraging, food storage, brood and nest maintenance, and some defense duties in certain species. Workers are the main caste in the colony for the digestion of cellulose in food and are the most likely to be found in infested wood. This is achieved in one of two ways. In all termite families, except the Termitidae, flagellate protists in the gut assist in cellulose digestion. However, in the Termitidae, which account for approximately 60% of all termite species, the flagellates have been lost and this digestive role is taken up, in part, by a consortium of prokaryotic organisms. This simple story, which has been in entomology textbooks for decades, is complicated by the finding that all studied termites can produce their own cellulase enzymes, and therefore might digest wood in the absence of their symbiotic microbes, although new evidence suggests these gut microbes make use of termite-produced cellulase enzymes. Our knowledge of the relationships between the microbial and termite parts of their digestion is still rudimentary. What is true in all termite species, however, is the workers feed the other members of the colony with substances derived from the digestion of plant material, either from the mouth or anus. This process of feeding of one colony member by another is known as trophallaxis, and is one of the keys to the success of the group. Trophallaxis is an effective method of nutritional tactics to converse and recycle components that are nitrogenous. It frees the parents from feeding all but the first generation of offspring, allowing for the group to grow much larger and ensuring the necessary gut symbionts are transferred from one generation to another. Some termite species do not have a true worker caste, instead relying on nymphs that perform the same work without differentiating as a separate caste.
The soldier caste has anatomical and behavioural specializations, providing strength and armour which are primarily useful against ant attacks. The proportion of soldiers within a colony varies both within and among species. Many soldiers have jaws so enlarged, they cannot feed themselves, but instead, like juveniles, are fed by workers. Simple holes in the forehead, fontanelles, exuding defensive secretions are a feature of the family Rhinotermitidae. Many species are readily identified using the characteristics of the soldiers' heads, mandibles, or nasi. Among the drywood termites, a soldier's globular (phragmotic) head can be used to block their narrow tunnels. Termite soldiers are usually blind, but in some families, particularly among the dampwood termites, soldiers developing from the reproductive line may have at least partly functional eyes.
The specialization of the soldier caste is principally a defence against predation by ants. Ants represent the single biggest threat to termite mounds and nests. Soldier Termite species armed with enlarged heads and powerful jaws can provide only limited defense and delay to a determined ant attack. Ants are more agile, often have functioning eyesight, and attack in an orchestrated and cooperative manner, for example Megaponera analis has a very sophisticated and successful raiding behaviour against termites. Termite soldiers are not evolved in this way, and defend the mound individually against multiple attacking ants resulting in an obvious and observable disadvantage. Ant species, such as the Formica, can deliver paralyzing stings in addition to their own powerful mandibles. Though powerful and formidable, many species of termite soldiers can provide only a suicidal delay to an ant invasion. However, it is one that observably results in preservation of the mound by industrious workers who react quickly to close off tunnels vital to access the deep interior of the mound. The wide range of jaw types and phragmotic heads provides methods that effectively block narrow termite tunnels against ant entry.
A tunnel-blocking soldier can rebuff attacks from many ants. Usually more soldiers stand by behind the initial soldier so once the first one falls another soldier will take the place. In cases where the intrusion is coming from a breach that is larger than the soldier's head, defence requires special formations where soldiers form a phalanx-like formation around the breach and bite at intruders or exude toxins from the nasus or fontanelle. This formation involves self-sacrifice because once the workers have repaired the breach during fighting, no return is provided, thus leading to the death of all defenders. Another form of self-sacrifice is performed by Southeast Asian tar baby termites (Globitermes sulphureus). The soldiers of this species commit suicide by autothysis—rupturing a large gland just beneath the surface of their cuticles. The thick, yellow fluid in the gland becomes very sticky on contact with the air, entangling ants or other insects which are trying to invade the nest.
Termites undergo incomplete metamorphosis. Freshly hatched young appear as tiny termites that grow without significant morphological changes (other than wings and soldier specializations). Some species of termites have dimorphic soldiers (up to three times the size of smaller soldiers). Though their value is unknown, they may function as an elite class that defends only the inner tunnels of the mound. Evidence for this is, even when provoked, these large soldiers do not defend themselves, but retreat deeper into the mound. On the other hand, dimorphic soldiers are common in some Australian species of Schedorhinotermes that neither build mounds nor appear to maintain complex nest structures. Some termite taxa are without soldiers; perhaps the best known of these are in the Apicotermitinae. The pantropical subfamily Nasutitermitinae have a different caste of soldiers with the ability to exude noxious liquids through a horn-like nozzle frontal projection (nasus), known as nasutes, that is used for defence. Nasutes eject a glue-like secretion as a form of defence, and they have lost their mandibles throughout the course of evolution; instead they have the ability to biosynthesize. Nitrogen fixation plays an important role in nutrition for nasutes.
Termites can be found globally with the exception of Antarctica. The diversity of termite species is low in North America and Europe (10 species known in Europe and 50 in North America), but the diversity of termites in South America numbers currently over 400. Of the 3,000 termite species currently classified, 1,000 of them are in Africa, where most mound species dominate the landscape. Approximately 1.1 million termite mounds can be found in the Kruger National Park alone. In Asia, there are 435 species of termites, mainly distributed in China. These species are restricted to specific habitats like tropical and subtropical habitats. In Australia, all ecological groups of termites (subterranean, drywood, harvester, and mound builders) are endemic to the country, with over 360 classified species.
Termites are usually small, measuring between 4 to 15 millimetres (0.16 to 0.59 in) in length, but the largest of all termites are the queens of the species Macrotermes bellicosus, measuring up to lengths over 10 centimetres (4 in). Globally, termites are found roughly between 50 degrees north and 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 (11%) of atmospheric methane, one of the prime greenhouse gases. Termites based on their ecological groups will have habitat preferences. For example, drywood termites will live in moist wood, where they receive moisture from the wood they feed on, and subterranean termites will live in damp soil. A particular species in this group is the West Indian Drywood termite (Cryptotermes brevis), which is known as an invasive species in Australia. They cause approximately $1000 million worth of damage each year in Australia alone. A $1 million eradication program is attempting to remove the pest.
|Asia||Africa||North America||South America||Europe||Australia|
|Estimated number of species||435||1,000||50||400||10||360|
Life cycle and reproduction
Like other social insects, most individuals in a termite colony are infertile workers, but unlike bees or ants, the worker termites are diploid individuals of both sexes and develop from fertilized eggs. By contrast female bees (both workers and the queen) are diploid and develop from fertilized eggs while males (drones) are haploid and develop from unfertilized eggs. The life cycle of a termite begins with an egg but differs from that of a bee or ant, going through a developmental process called incomplete metamorphosis, with egg, nymph and adult stages. When eggs hatch into nymphs, they will go through a series of moults until they become adults. In some species, eggs will go through four moulting stages while nymphs will go through three. Nymphs first moult into workers, and then later on some workers will go through further moulting and become soldiers or become alates, only by moulting into alate nymphs.
Some workers and nymphs are capable of becoming supplementary reproductives and take over the primary role of a king or queen if they die. Nymph development into adults can take months, although this depends on food, temperature and the general population of the colony. Since nymphs are unable to feed themselves, workers feed them instead, but they also take part in the social life in the colony, and have certain tasks they must do. Pheromones are said to regulate the caste system in termite colonies, which prevents other termites from becoming fertile queens themselves.[non-primary source needed]
Termite alates only leave the colony when nuptial flight takes place. Alate males and females will pair up together then land afterwards in search of a suitable place for a colony. Termites will not mate until the king and queen find a suitable spot for their colony, then excavate a chamber big enough for both, close up the entrance and proceed to mate. After mating, the pair will never go outside and spend the rest of their lives in their nest. The queen will only lay 10-20 eggs in the very early stages of the colony, but will increase to as many as 1,000 a day when the colony is several years of age. Subterranean termites have nuptial flights in many different times, depending on the species. Some species will begin flight season in December until February, while some will begin flight from January to April and February to May. Some flights will take place on a warm day after rainfall, while some will swarm during the nighttime. Termite colonies observed in the U.S. state of Virginia are said to hold at least 60,000 individuals, with underground networks connecting to other nests that are apart of the colony.
Ecologically, termites are important in nutrient recycling, habitat creation, soil formation and quality and, particularly the winged reproductives, as food for countless predators. The role of termites in hollowing timbers and thus providing shelter and increased wood surface areas for other creatures is critical for the survival of a large number of timber-inhabiting species. Larger termite mounds play a role in providing a habitat for plants and animals, especially on plains in Africa that are seasonally inundated by a rainy season, providing a retreat above the water for smaller animals and birds, and a growing medium for woody shrubs with root systems that cannot withstand inundation for several weeks. In addition, scorpions, lizards, snakes, small mammals, and birds live in abandoned or weathered mounds, and aardvarks dig substantial caves and burrows in them, which may then become homes for animals such as hyenas and mongooses.
As detritivores, termites clear away leaf and woody litter and so reduce the severity of the annual bush fires in African savannas, which are not as destructive as those in Australia and the U.S.A. Their role in bioturbation on the Khorat Plateau is under investigation.
Termites are generally grouped according to their nesting and feeding habits. Therefore the commonly used general groupings are subterranean, soil-dwelling, drywood, dampwood, and grass-eating. Of these, subterraneans and drywoods are primarily responsible for damage to human-made structures.
All termites eat cellulose in its various forms as plant fibre. Cellulose is a rich energy source (as demonstrated by the amount of energy released when wood is burned), but remains difficult to digest. Termites rely primarily upon symbiotic protozoa (metamonads) such as Trichonympha, and other microbes in their guts to digest the cellulose for them and absorb the end products for their own use. Gut protozoa, such as Trichonympha, 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 and primarily rely upon the bacteria. Owing to closely related bacterial species, it is strongly presumed that the termites' gut flora are descended from the gut flora of the ancestral wood-eating cockroaches, like those of the genus Cryptocercus. In one study, it found particular termite species' prefer poplar and maple woods the most in comparison to other woods that were generally rejected by termite colonies.
Some species of termite practice fungiculture. They maintain a “garden” of specialized fungi of genus Termitomyces, which are nourished by the excrement of the insects. When the fungi are eaten, their spores pass undamaged through the intestines of the termites to complete the cycle by germinating in the fresh faecal pellets. They are also well known for eating smaller insects in a last resort environment. A recent study by Australian scientists found that termites have been found to accumulate trace amounts of gold in their nests. According to the CSIRO, the termites burrow beneath weathered surface material which typically masks human attempts to find gold, and brings indicators of deposits to the surface. They believe that studying termite nests may lead to less invasive methods of finding gold deposits.
Plant defences against termites
Many plants have developed effective defences against termites, and in most ecosystems, there is an observable balance between the growth of plants and the feeding of termites. Defence is typically achieved by secreting anti-feedant chemicals (such as oils, resins, and lignins) into the woody cell walls. This reduces the ability of termites to efficiently digest the cellulose. Many of the strongly termite-resistant tree species have heartwood timber that is extremely dense (such as Eucalyptus camaldulensis) due to accretion of these resins. Over the years there has been considerable research into these natural defensive chemicals with scientists seeking to add them to timbers from susceptible trees. A commercial product, “Blockaid,” has been developed in Australia and uses a range of plant extracts to create a paint-on nontoxic termite barrier for buildings. In 2005 a group of Australian scientists “discovered” (announced) a treatment based on an extract of a species of Eremophila that repels termites. Tests have shown that termites are strongly repelled by the toxic material to the extent that they will starve rather than consume cross treated samples. When kept close to the extract, they become disoriented and eventually die. Scientists hoped to use this toxic compound commercially as a soil barrier but it failed field testing.
Termite workers build and maintain nests which house the colony. These are elaborate structures made using a combination of soil, mud, chewed wood/cellulose, saliva, and faeces. A nest has many functions such as providing a protected living space and water conservation (through controlled condensation). There are nursery chambers deep within the nest where eggs and first instar larvae are tended. Some species maintain fungal gardens that are fed on collected plant matter, providing a nutritious mycelium on which the colony then feeds (see Diet, above). Nests are punctuated by a maze of tunnel-like galleries that provide air conditioning and control the CO2/O2 balance, as well as allow the termites to move through the nest.
Nests are commonly built underground, in large pieces of timber, inside fallen trees, or atop living trees. Some species build nests above ground, and they can develop into mounds. Homeowners need to be careful of tree stumps that have not been dug up. These are prime candidates for termite nests and being close to homes, termites usually end up destroying the siding and sometimes even wooden beams.
Some species build complex nests called polycalic nests. This habitat of forming polycalic nests is called polycalism. Polycalic species of termites form multiple nests, or calies, connected by subterranean chambers. All four subfamilies of the Termitidae are known to have polycalic species. This habit can make control difficult because when one nest is eliminated, re-infestation can easily occur via the underground connections to other nests. Polycalic nests appear to be less frequent in mound building species, although polycalic arboreal nests have been observed in a few species of the Microcerotermes and several species of Nasutitermes.
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Mounds (also known as "termitaria") occur when an aboveground nest grows beyond its initially concealing surface. They are commonly called “ant hills” in Africa and Australia, despite the technical incorrectness of that name.
In tropical savannas, the mounds may be very large, with an extreme of 9 m (29.5 ft) high in the case of large conical mounds constructed by some Macrotermes species in well-wooded areas in Africa. Two to three metres, however, would be typical for the largest mounds in most savannas. The shape ranges from somewhat amorphous domes or cones usually covered in grass and/or woody shrubs, to sculptured hard-earth mounds, or a mixture of the two. Despite the irregular mound shapes, the different species in an area can usually be identified by simply looking at the mounds.
The sculptured mounds sometimes have elaborate and distinctive forms, such as those of the compass termite (Amitermes meridionalis and A. laurensis) which build tall, wedge-shaped mounds with the long axis oriented approximately north–south, which gives them their common name. This orientation has been experimentally shown to assist thermoregulation. The thin end of the nest faces towards the sun at its peak intensity, hence taking up the least possible heat, and allows these termites to stay above ground where other species are forced to move into deeper below ground areas. This also allows the compass termites to live in poorly drained areas where other species would be caught between a choice of baking or drowning. The column of hot air rising in the aboveground mounds helps drive air circulation currents inside the subterranean network. The structure of these mounds can be quite complex. The temperature control is essential for those species that cultivate fungal gardens and even for those that do not; much effort and energy is spent maintaining the brood within a narrow temperature range, often only plus or minus 1° Celsius over a day.
In some parts of the African savanna, a high density of aboveground mounds dominates the landscape. For instance, in some parts of the Busanga Plain area of Zambia, small mounds of about 1 m diameter with a density of about 100 per hectare can be seen on grassland between larger tree- and bush-covered mounds about 25 m in diameter with a density around 1 per hectare, and both show up well on high-resolution satellite images taken in the wet season.
Termite mound in Queensland / Australia
Termites are weak and relatively fragile insects that need to stay moist to survive. They can be overpowered by ants and other predators when exposed. They avoid these perils by covering their trails with tubing (known as "mud tunnels") made of feces, plant matter, saliva, and soil. Thus, the termites can remain hidden and wall out unfavourable environmental conditions. Sometimes these shelter tubes will extend for many metres, such as up the outside of a tree reaching from the soil to dead branches.
To subterranean termites, any breach of their tunnels or nests is a cause for alarm. When the Formosan subterranean termite (Coptotermes formosanus) and the eastern subterranean termite (Reticulitermes flavipes) detect a potential breach, the soldiers will usually bang their heads apparently to attract other soldiers for defence and recruit additional workers to repair any breach. This head-banging response to vibration is also useful when attempting to locate termites in house frames.
Owing to their wood-eating habits, many termite species can do great damage to unprotected 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 to wood; they also damage paper, cloth, carpets, and other cellulosic materials. Particles taken from soft plastics, plaster, rubber, and sealants such as silicone rubber and acrylics are often employed in gallery construction. Humans have moved many wood-eating species between continents, but have also caused drastic population decline in others through habitat loss and pesticide application. Termites are commonly viewed as pests in many countries, because of the damage they can cause to structures and similar nuisances. In April 2011, wood-eating termites were blamed for reportedly consuming more than $220,000 worth of Indian rupee notes.
Avoiding contact of susceptible timber with the ground by using termite-resistant concrete, steel, or masonry foundations with appropriate barriers is an effective method of preventing timber damage. Termites are able to bridge these with shelter tubes, and it has been known for termites to chew through piping made of soft plastics and even some metals, such as lead, to exploit moisture. In general, new buildings should be constructed with embedded physical termite barriers so no easy means remain for termites to gain concealed entry. While barriers of poisoned soil, so-called termite pre-treatment, have been in general use since the 1970s, it is preferable that these be used only for existing buildings without effective physical barriers. The intent of termite barriers (whether physical, poisoned soil, or some of the new poisoned plastics) is to prevent the termites from gaining unseen access to structures. In most instances, termites attempting to enter a barriered building will be forced into the less favourable approach of building shelter tubes up the outside walls; thus, they can be clearly visible both to the building occupants and a range of predators. Use of timber that is naturally resistant to termites, such as Syncarpia glomulifera (turpentine tree), Tectona grandis (teak), Callitris glaucophylla (white cypress), or one of the sequoias. No tree species has every individual tree yielding only timbers that are immune to termite damage, so even with well-known termite-resistant timber types, pieces occasionally will be attacked.
When termites have already penetrated a building, the first action is usually to destroy the colony with insecticides before removing the termites' means of access and fixing the problems that encouraged them in the first place. Baits (feeder stations) with small quantities of disruptive insect hormones or other very slow-acting toxins have become the preferred, least-toxic management tool in most western countries. This has replaced the dusting of toxins direct into termite tunnels that had been widely done since the early 1930s (originating in Australia). The main dust toxicants have been the inorganic metallic poison arsenic trioxide, insect growth regulators (hormones such as triflumuron), and more recently fipronil, a phenyl-pyrazole. Blowing dusts into termite workings is a highly skilled process. All these slow-acting poisons can be distributed by the workers for hours or weeks before any symptoms occur and are capable of destroying the entire colony. More modern variations include chlorfluazuron, diflubenzuron, hexaflumuron, and novaflumuron as bait toxicants, and fipronil, imidacloprid, and chlorantraniprole as soil poisons. Soil poisons are the least-preferred method of control, as this requires large doses of toxin and results in uncontrollable release to the environment. Ecofriendly termite control with neem oil has recently been found both economical and effective. Termite attack can be averted by application of fluidized neem seed oil by spraying on plantation, painting cleaned wooden articles and dropping at the base of termite tunnels.
The termites' effects are damaging, costing the southwestern United States approximately $1.5 billion each year in wood structure damage. To better control the population of termites, researchers at the Agricultural Research Service have found a way to track the movement of the destructive pests. In 1990, researchers found a way to safely and reliably track termites using immunoglobulin G (IgG) marker proteins from rabbits or chickens. In field tests, termite bait was laced with the rabbit IgG and the termites were randomly exposed to feeding on this bait. Termites were later collected from the field and tested for the rabbit-IgG markers using a rabbit-IgG-specific assay. However, this method of testing for the tracking proteins is expensive. Recently, researchers have developed a new way of tracking the termites using egg white, cow milk, or soy milk proteins, which can be sprayed on the termites in the field. This new method is less expensive because the proteins can be traced using a protein-specific ELISA test. The ELISA test is more affordable, because it is designed for mass production. Researchers hope to use this method of tracking termites to find a more cost-effective way to control the damaging pests.
Termites in the human diet
Termites are consumed by many different cultures around the world, and in Africa, the alates are an important factor in the diets of native populations. Tribes have different methods and ways of collecting or cultivate insects, and sometimes tribes will collect soldiers from several species. Queens are harder to acquire, but queens are regarded as a delicacy if they are able to be collected. Termite alates are high in nutrition levels, due to the fact they have adequate levels of fat and protein and are also regarded as pleasant in taste, having a nut-like flavour after they are cooked.
Alates are collected when the rainy season begins. During nuptial flight, they can be typically seen around lights as they are attracted to them, and so nets are set up on lamps and are later collected. The wings are shed and a technique that is similar to winnowing is performed. The best result comes when they are roasted in a gentle fashion on a hot plate or fried until they show signs of being crisp; oil is not required as their bodies usually contain sufficient amounts of oil. Termites are typically eaten if livestock is lean and tribal crops have not yet developed or produced any food, or if food stock from previous growing seasons is limited.
Termites are consumed in other countries and continents, although this is usually limited to local or tribal areas in Asia and North and South America in comparison to its consumption in Africa. In Australia, indigenous Australians communities are aware termites are edible, but are not consumed, even if they are facing harsh times. There are limited sources as to why they show limited interest to the consumption of the alates, workers and soldier termites. Termites contribute to human nutrition via consumption of the soil, commonly known as geophagy. Termitaria (termite mounds) are the main sources of soil consumption in multiple countries including Kenya, Tanzania, Zambia, Zimbabwe and South Africa.
Termites can be major agricultural pests, particularly in East Africa and North Asia, where crop losses can be severe (3-100%) in crop loss in Africa). Counterbalancing this is the greatly improved water infiltration where termite tunnels in the soil allow rainwater to soak in deeply and help reduce runoff and consequent soil erosion through bioturbation.
Termites and architecture
The Eastgate Centre, Harare, is a shopping centre and office block in central Harare, Zimbabwe, whose architect, Mick Pearce, used passive cooling inspired by that being used by the local termites. Termite mounds include flues that vent through the top and sides, and the mound itself is designed to catch the breeze. As the wind blows, hot air from the main chambers below ground is drawn out of the structure, helped by termites opening or blocking tunnels to control air flow.
As an energy source
The U.S. Department of Energy is researching ways to replace fossil fuels with renewable sources of cleaner energy, and termites are considered a possible way to reach this goal through metagenomics.
Termites may produce up to two litres of hydrogen from digesting a single sheet of paper, making them one of the planet’s most efficient bioreactors. Termites achieve this high degree of efficiency by exploiting the metabolic capabilities of about 200 different species of microbes that inhabit their hindguts. The microbial community in the termite gut efficiently manufactures large quantities of hydrogen; the complex lignocellulose polymers within wood are broken down into simple sugars by fermenting bacteria in the termite’s gut, using enzymes that produce hydrogen as a byproduct. A second wave of bacteria uses the simple sugars and hydrogen to make the acetate the termite requires for energy. By sequencing the termite's microbial community, the DOE hopes to get a better understanding of these biochemical pathways. If it can be determined which enzymes are used to create hydrogen, and which genes produce them, this process could potentially be scaled up with bioreactors to generate hydrogen from woody biomass, such as poplar, in commercial quantities.
Skeptics regard this as unlikely to become a carbon-neutral commercial process owing to the energy inputs required to maintain the system. For decades, researchers have sought to house termites on a commercial scale (like worm farms) to break down woody debris and paper, but funding has been scarce, and the problems of developing a continuous process that does not disrupt the termites' homeostasis have not been overcome.
Few zoos hold termites, due to the difficulty in keeping them captive and to the reluctance of authorities to permit potential pests. One of the few that do, Zoo Basel in Switzerland, has two thriving African termite (Macrotermes bellicosus) population - resulting in very rare (in captivity) mass migrations of young flying termites. This happened in September 2008, when thousands of male termites left their mound each night, died, and covered the floors and water pits of the house holding their exhibit.
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- Amitermes floridensis , Florida darkwinged subterranean termite
- Coptotermes formosanus , Formosan subterranean termite
- Coptotermes gestroi, Asian subterranean termite
- Cryptotermes brevis, West Indian drywood termite
- Heterotermes sp., West Indian subterranean termite
- Cryptotermes cavifrons, a drywood termite
- Incisitermes minor, western drywood termite
- Neotermes spp., Florida dampwood termites
- Prorhinotermes simplex, Cuban subterranean termite
- Reticulitermes spp., native U.S.A. subterranean termites