ISOPTERA (TERMITES) ORDER DESCRIPTION

Termites are eusocial insects that are classified at the taxonomic rank of infraorder Isoptera, or as epifamily Termitoidae within the cockroach order Blattodea. Termites were once classified in a separate order from cockroaches, but recent phylogenetic studies indicate that they evolved from close ancestors of cockroaches during the Jurassic or Triassic. However, the first termites possibly emerged during the Permian or even the Carboniferous. About 3,106 species are currently described, with a few hundred more left to be described. Although these insects are often called white ants, they are not ants.

Like ants and some bees and wasps from the separate order Hymenoptera, termites divide labour among castes consisting of sterile male and female "workers" and "soldiers". All colonies have fertile males called "kings" and one or more fertile females called "queens". Termites mostly feed on dead plant material and cellulose, generally in the form of wood, leaf litter, soil, or animal dung. Termites are major detritivores, particularly in the subtropical and tropical regions, and their recycling of wood and plant matter is of considerable ecological importance.

Termites are among the most successful groups of insects on Earth, colonising most landmasses except for Antarctica. Their colonies range in size from a few hundred individuals to enormous societies with several million individuals. Termite queens have the longest lifespan of any insect in the world, with some queens living up to 50 years. Unlike ants, which undergo a complete metamorphosis, each individual termite goes through an incomplete metamorphosis that proceeds through egg, nymph, and adult stages. Colonies are described as superorganisms because the termites form part of a self-regulating entity: the colony itself.

Termites are a delicacy in the diet of some human cultures and are used in many traditional medicines. Several hundred species are economically significant as pests that can cause serious damage to buildings, crops, or plantation forests. Some species, such as the West Indian drywood termite (Cryptotermes brevis), are regarded as invasive species.

Taxonomy and evolution:
The giant northern termite is the most primitive living termite. Its body plan has been described as a cockroach's abdomen stuck to a termite's fore part. Its wings have the same form as roach wings, and like roaches, it lays its eggs in a case.
DNA analysis from 16S rRNA sequences has supported a hypothesis, originally suggested by Cleveland and colleagues in 1934, that these insects are most closely related to wood-eating cockroaches (genus Cryptocercus, the woodroach). This earlier conclusion had been based on the similarity of the symbiotic gut flagellates in the wood-eating cockroaches to those in certain species of termites regarded as living fossils. In the 1960s additional evidence supporting that hypothesis emerged when F. A. McKittrick noted similar morphological characteristics between some termites and Cryptocercus nymphs. These similarities have led some authors to propose that termites be reclassified as a single family, the Termitidae, within the order Blattodea, which contains cockroaches.[9][10] Other researchers advocate the more conservative measure of retaining the termites as the 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, but given the diversity of Cretaceous termites and early fossil records showing mutualism between microorganisms and these insects, they likely originated earlier in the Jurassic or Triassic. Further evidence of a Jurassic origin is the assumption that the extinct Fruitafossor consumed termites, judging from its morphological similarity to modern termite-eating mammals. The oldest termite nest discovered is believed to be from the Upper Cretaceous in West Texas, where the oldest known faecal pellets were also discovered.

Claims that termites emerged earlier have faced controversy. For example, F. M. Weesner indicated that the Mastotermitidae termites may go back to the Late Permian, 251 million years ago, and fossil wings that have a close resemblance to the wings of Mastotermes of the Mastotermitidae, the most primitive living termite, have been discovered in the Permian layers in Kansas. It is even possible that the first termites emerged during the Carboniferous. Termites are thought to be the descendants of the genus Cryptocercus. The folded wings of the fossil wood roach Pycnoblattina, arranged in a convex pattern between segments 1a and 2a, resemble those seen in Mastotermes, the only living insect with the same pattern. Krishna et al., though, consider that all of the Paleozoic and Triassic insects tentatively classified as termites are in fact unrelated to termites and should be excluded from the Isoptera. Termites were the first social insects to evolve a caste system, evolving more than 100 million years ago.
Termites have long been accepted to be closely related to cockroaches and mantids, and they are classified in the same superorder (Dictyoptera). Strong evidence suggests termites are highly specialised wood-eating cockroaches. The cockroach genus Cryptocercus shares the strongest phylogenetical similarity with termites and is considered to be a sister-group to termites. Termites and Cryptocercus share similar morphological and social features: for example, most cockroaches do not exhibit social characteristics, but Cryptocercus takes care of its young and exhibits other social behaviour such as trophallaxis and allogrooming. The primitive giant northern termite (Mastotermes darwiniensis) exhibits numerous cockroach-like characteristics that are not shared with other termites, such as laying its eggs in rafts and having anal lobes on the wings. Cryptocercidae and Isoptera are united in the clade Xylophagodea. Although termites are sometimes called "white ants", they are actually not ants. Ants belong to the family Formicidae within the order Hymenoptera. The similarity of their social structure to that of termites is attributed to convergent evolution.

As of 2013, about 3,106 living and fossil termite species are recognised, classified in 12 families. The infraorder Isoptera is divided into the following clade and family groups, showing the subfamilies in their respective classification:
Order Blattaria

Infraorder Isoptera
Family †Cratomastotermitidae
Family Mastotermitidae
Parvorder Euisoptera
Family Termopsidae
Family Archotermopsidae
Family Hodotermitidae
Family Stolotermitidae
Stolotermitinae
Porotermitinae
Family Kalotermitidae
Nanorder Neoisoptera
Family †Archeorhinotermitidae
Family Stylotermitidae
Family Rhinotermitidae
Coptotermitinae
Heterotermitinae
Prorhinoterminae
Psammotermitinae
Rhinotermitinae
Termitogetoninae
Family Serritermitidae
Family Termitidae
Sphaerotermitinae
Macrotermitinae
Foraminitermitinae
Apicotermitinae
Syntermitinae
Nasutitermitinae
Cubitermitinae
Termitinae

Distribution and diversity
Termites are found on all continents except Antarctica. The diversity of termite species is low in North America and Europe (10 species known in Europe and 50 in North America), but is high in South America, where over 400 species are known. Of the 3,000 termite species currently classified, 1,000 are found in Africa, where mounds are extremely abundant in certain regions. Approximately 1.1 million active termite mounds can be found in the northern Kruger National Park alone. In Asia, there are 435 species of termites, which are mainly distributed in China. Within China, termite species are restricted to mild tropical and subtropical habitats south of the Yangtze River. In Australia, all ecological groups of termites (dampwood, drywood, subterranean) are endemic to the country, with over 360 classified species.

Due to their soft cuticles, termites do not inhabit cool or cold habitats. There are three ecological groups of termites: dampwood, drywood and subterranean. Dampwood termites are found only in coniferous forests, and drywood termites are found in hardwood forests; subterranean termites live in widely diverse areas. One species in the drywood group is the West Indian drywood termite (Cryptotermes brevis), which is an invasive species in Australia.

Description
Termites are usually small, measuring between 4 to 15 millimetres (0.16 to 0.59 in) in length.The largest of all extant termites are the queens of the species Macrotermes bellicosus, measuring up to over 10 centimetres (4 in) in length. Another giant termite, the extinct Gyatermes styriensis, flourished in Austria during the Miocene and had a wingspan of 76 millimetres (3.0 in) and a body length of 25 millimetres (0.98 in).]

Most worker and soldier termites are completely blind as they do not have a pair of eyes. However, some species, such as Hodotermes mossambicus, have compound eyes which they use for orientation and to distinguish sunlight from moonlight. The alates have eyes along with lateral ocelli. Lateral ocelli, however, are not found in all termites. Like other insects, termites have a small tongue-shaped labrum and a clypeus; the clypeus is divided into a postclypeus and anteclypeus. Termite antennae have a number of functions such as the sensing of touch, taste, odours (including pheromones), heat and vibration. The three basic segments of a termite antenna include a scape, a pedicel (typically shorter than the scape), and the flagellum (all segments beyond the scape and pedicel).The mouth parts contain a maxillae, a labium, and a set of mandibles. The maxillae and labium have palps that help termites sense food and handling.

Consistent with all insects, the anatomy of the termite thorax consists of three segments: the prothorax, the mesothorax and the metathorax.[39] Each segment contains a pair of legs. On alates, the wings are located at the mesothorax and metathorax. The mesothorax and metathorax have well-developed exoskeletal plates; the prothorax has smaller plates.

Termites have a ten-segmented abdomen with two plates, the tergites and the sternites. The tenth abdominal segment has a pair of short cerci. There are ten tergites, of which nine are wide and one is elongated. The reproductive organs are similar to those in cockroaches but are more simplified. For example, the intromittent organ is not present in male alates, and the sperm is either immotile or aflagellate. However, Mastotermitidae termites have multiflagellate sperm with limited motility. The genitals in females are also simplified. Unlike in other termites, Mastotermitidae females have an ovipositor, a feature strikingly similar to that in female cockroaches.

The non-reproductive castes of termites are wingless and rely exclusively on their six legs for locomotion. The alates fly only for a brief amount of time, so they also rely on their legs. The appearance of the legs is similar in each caste, but the soldiers have larger and heavier legs. The structure of the legs is consistent with other insects: the parts of a leg include a coxa, trochanter, femur, tibia and the tarsus. The number of tibial spurs on an individual's leg varies. Some species of termite have an arolium, located between the claws, which is present in species that climb on smooth surfaces but is absent in most termites.

Unlike in ants, the hind-wings and fore-wings are of equal length. Most of the time, the alates are poor flyers; their technique is to launch themselves in the air and fly in a random direction. Studies show that in comparison to larger termites, smaller termites cannot fly long distances. When a termite is in flight, its wings remain at a right angle, and when the termite is at rest, its wings remain parallel to the body.

Caste system

Caste system of termites
A — King
B — Queen
C — Secondary queen
D — Tertiary queen
E — Soldiers
F — Worker
Worker termites undertake the most labour within the colony, being responsible for foraging, food storage, and brood and nest maintenance. Workers are tasked with the digestion of cellulose in food and are thus the most likely caste to be found in infested wood. The process of worker termites feeding other nestmates is known as trophallaxis. Trophallaxis is an effective nutritional tactic to convert and recycle nitrogenous components. It frees the parents from feeding all but the first generation of offspring, allowing for the group to grow much larger and ensuring that 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 specialisations, and their sole purpose is to defend the colony. Many soldiers have large heads with highly modified powerful jaws so enlarged they cannot feed themselves. Instead, like juveniles, they are fed by workers. Fontanelles, simple holes in the forehead that exude defensive secretions, are a feature of the family Rhinotermitidae. Many species are readily identified using the characteristics of the soldiers' larger and darker head and large mandibles. Among certain termites, soldiers may use their globular (phragmotic) heads to block their narrow tunnels. Different sorts of soldiers include minor and major soldiers, and nasutes, which have a horn-like nozzle frontal projection (a nasus). These unique soldiers are able to spray noxious, sticky secretions containing diterpenes at their enemies. Nitrogen fixation plays an important role in nasute nutrition.

The reproductive caste of a mature colony includes a fertile female and male, known as the queen and king. The queen of the colony is responsible for egg production for the colony. Unlike in ants, the king mates with her for life. In some species, the abdomen of the queen swells up dramatically to increase fecundity, a characteristic known as physogastrism. Depending on the species, the queen will start producing reproductive winged alates at a certain time of the year, and huge swarms emerge from the colony when nuptial flight begins. These swarms attract a wide variety of predators.

Life cycle
A termite nymph looks like a smaller version of an adult but lacks the specialisations that would enable identification of its caste.
A young termite nymph. Nymphs first moult into workers, but others may further moult to become soldiers or alates.
Termites are often compared with the social Hymenoptera (ants and various species of bees and wasps), but their differing evolutionary origins result in major differences in life cycle. In the eusocial Hymenoptera, the workers are exclusively female: males (drones) are haploid and develop from unfertilised eggs, while females (both workers and the queen) are diploid and develop from fertilised eggs. In contrast, worker termites, which constitute the majority in a colony, are diploid individuals of both sexes and develop from fertilised eggs. Depending on species, male and female workers may have different roles in a termite colony.

The life cycle of a termite begins with an egg, but is different from that of a bee or ant in that it goes through a developmental process called incomplete metamorphosis, with egg, nymph and adult stages. Nymphs resemble small adults, and go through a series of moults as they grow. In some species, eggs go through four moulting stages and nymphs go through three. Nymphs first moult into workers, and then some workers go through further moulting and become soldiers or alates; workers become alates only by moulting into alate nymphs.

The development of nymphs into adults can take months; the time period depends on food availability, temperature, and the general population of the colony. Since nymphs are unable to feed themselves, workers must feed them, but workers also take part in the social life of the colony and have certain other tasks to accomplish such as foraging, building or maintaining the nest or tending to the queen. Pheromones regulate the caste system in termite colonies, preventing all but a very few of the termites from becoming fertile queens.

Reproduction
Termite alates only leave the colony when a nuptial flight takes place. Alate males and females will pair up together and then land in search of a suitable place for a colony. A termite king and queen will not mate until they find such a spot. When they do, they excavate a chamber big enough for both, close up the entrance and proceed to mate. After mating, the pair will never go outside and will spend the rest of their lives in the nest. Nuptial flight time varies in each species. For example, alates in certain species emerge during the day in summer while others emerge during the winter. The nuptial flight may also begin at dusk, when the alates swarm around areas with lots of lights. The time when nuptial flight begins depends on the environmental conditions, the time of day, moisture, wind speed and precipitation. The number of termites in a colony also varies, with the larger species typically having 100–1,000 individuals. However, some termite colonies, including those with large individuals, can number in the millions.

The queen will only lay 10–20 eggs in the very early stages of the colony, but will lay as many as 1,000 a day when the colony is several years old. 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 40,000 eggs a day. The two mature ovaries may have some 2,000 ovarioles each.[69] The abdomen increases the queen's body length to several times more than before mating and reduces her ability to move freely; attendant workers provide assistance.

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.[59] If a queen is absent, a termite king will produce pheromones which encourage the development of replacement termite queens.[70] As the queen and king are monogamous, sperm competition does not occur.

Termites going through incomplete metamorphosis on the path to becoming alates form a subcaste in certain species of termite, functioning as potential supplementary reproductives. These supplementary reproductives only mature into primary reproductives upon the death of a king or queen, or when the primary reproductives are separated from the colony. Supplementaries have the ability to replace a dead primary reproductive, and there may also be more than a single supplementary within a colony.[50] Some queens have the ability to switch from sexual reproduction to asexual reproduction. Studies show that while termite queens mate with the king to produce colony workers, the queens reproduce their replacements (neotenic queens) parthenogenetically.

Behaviour and ecology
Diet
Termites are detritivores, consuming dead plants at any level of decomposition. They also play a vital role in the ecosystem by recycling waste material such as dead wood, faeces and plants. Many species eat cellulose, having a specialised midgut that breaks down the fibre.[78] Termites are considered to be a major source (11%) of atmospheric methane, one of the prime greenhouse gases, produced from the breakdown of cellulose.[79] Termites rely primarily upon symbiotic protozoa (metamonads) and other microbes such as flagellate protists in their guts to digest the cellulose for them, allowing them to 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. Most higher termites, especially in the family Termitidae, can produce their own cellulase enzymes, but they rely primarily upon the bacteria. The flagellates have been lost in TermitidaE. Scientists' understanding of the relationship between the termite digestive tract and the microbial endosymbionts is still rudimentary; what is true in all termite species, however, is that the workers feed the other members of the colony with substances derived from the digestion of plant material, either from the mouth or anus. Judging from closely related bacterial species, it is strongly presumed that the termites' and cockroach's gut microbiota derives from their dictyopteran ancestors.

Certain species such as Gnathamitermes tubiformans have seasonal food habits. For example, they may preferentially consume Red three-awn (Aristida longiseta) during the summer, Buffalograss (Buchloe dactyloides) from May to August, and blue grama Bouteloua gracilis during spring, summer and autumn. Colonies of G. tubiformans consume less food in spring than they do during autumn when their feeding activity is high.

Various woods differ in their susceptibility to termite attack; the differences are attributed to such factors as moisture content, hardness, and resin and lignin content. In one study, the drywood termite Cryptotermes brevis strongly preferred poplar and maple woods to other woods that were generally rejected by the termite colony. These preferences may in part have represented conditioned or learned behaviour.

Some species of termite practice fungiculture. They maintain a "garden" of specialised 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. Molecular evidence suggests that the family Macrotermitinae developed agriculture about 31 million years ago. It is assumed that more than 90 percent of dry wood in the semiarid savannah ecosystems of Africa and Asia are reprocessed by these termites. Originally living in the rainforest, fungus farming allowed them to colonise the African savannah and other new environments, eventually expanding into Asia.

Depending on their feeding habits, termites are placed into two groups: the lower termites and higher termites. The lower termites predominately feed on wood. As wood is difficult to digest, termites prefer to consume fungus-infected wood because it is easier to digest and the fungi are high in protein. Meanwhile, the higher termites consume a wide variety of materials, including faeces, humus, grass, leaves and roots. The gut in the lower termites contains many species of bacteria along with protozoa, while the higher termites only have a few species of bacteria with no protozoa.

Predators
Termites are consumed by a wide variety of predators. One species alone, Hodotermes mossambicus, was found in the stomach contents of 65 birds and 19 mammals. Arthropods and reptiles such as bees, centipedes, cockroaches, crickets, dragonflies, frogs, lizards, scorpions, spiders, and toads consume these insects, while two spiders in the family Ammoxenidae are specialist termite predators. Other predators include aardvarks, aardwolves, anteaters, bats, bears, bilbies, many birds, echidnas, foxes, galagos, numbats, mice and pangolins. The aardwolf is an insectivorous mammal that primarily feeds on termites; it locates its food by sound and also by detecting the scent secreted by the soldiers; a single aardwolf is capable of consuming thousands of termites in a single night by using its long, sticky tongue. Sloth bears break open mounds to consume the nestmates, while chimpanzees have developed tools to "fish" termites from their nest. Wear pattern analysis of bone tools used by the early hominin Paranthropus robustus suggests that they used these tools to dig into termite mounds.


A Matabele ant (Megaponera analis) kills a Macrotermes bellicosus termite soldier during a raid.
Among all predators, ants are the greatest enemy to termites. Some ant genera are specialist predators of termites. For example, Megaponera is a strictly termite-eating (termitophagous) genus that perform raiding activities, some lasting several hours. Paltothyreus tarsatus is another termite-raiding species, with each individual stacking as many termites as possible in its mandibles before returning home, all the while recruiting additional nestmates to the raiding site through chemical trails. The Malaysian basicerotine ant Eurhopalothrix heliscata uses a different strategy of termite hunting by pressing themselves into tight spaces, as they hunt through rotting wood housing termite colonies. Once inside, the ants seize their prey by using their short but sharp mandibles.Tetramorium uelense is a specialised predator species that feeds on small termites. A scout will recruit 10–30 workers to an area where termites are present, killing them by immobilising them with their stinger. Centromyrmex and Iridomyrmex colonies sometimes nest in termite mounds, and so the termites are preyed on by these ants. No evidence for any kind of relationship (other than a predatory one) is known. Other ants, including Acanthostichus, Camponotus, Crematogaster, Cylindromyrmex, Leptogenys, Odontomachus, Ophthalmopone, Pachycondyla, Rhytidoponera, Solenopsis and Wasmannia, also prey on termites. In contrast to all these ant species, and despite their enormous diversity of prey, Dorylus ants rarely consume termites.

Ants are not the only invertebrates that perform raids. Many sphecoid wasps and several species including Polybia Lepeletier and Angiopolybia Araujo are known to raid termite mounds during the termites' nuptial flight.

Parasites, pathogens and viruses
Termites are less likely to be attacked by parasites than bees, wasps and ants, as they are usually well protected in their mounds. Nevertheless, termites are infected by a variety of parasites. Some of these include dipteran flies, Pyemotes mites, and a large number of nematode parasites. Most nematode parasites are in the order Rhabditida; others are in the genus Mermis, Diplogaster aerivora and Harteria gallinarum. Under imminent threat of an attack by parasites, a colony may migrate to a new location. Fungi pathogens such as such as Aspergillus nomius and Metarhizium anisopliae are, however, major threats to a termite colony as they are not host-specific and may infect large portions of the colony; transmission usually occurs via direct physical contact. M. anispliae is known to weaken the termite immune system. Infection with A. nomius only occurs when a colony is under great stress. Inquilinism between two termite species does not occur in the termite world.
Termites are infected by viruses including Entomopoxvirinae and the Nuclear Polyhedrosis Virus.

Locomotion and foraging
Because the worker and soldier castes lack wings and thus never fly, and the reproductives use their wings for just a brief amount of time, termites predominantly rely upon their legs to move about.

Foraging behaviour depends on the type of termite. For example, certain species feed on the wood structures they inhabit, and others harvest food that is near the nest. Most workers are rarely found out in the open, and do not forage unprotected; they rely on sheeting and runways to protect them from predators.[49] Subterranean termites construct tunnels and galleries to look for food, and workers who manage to find food sources recruit additional nestmates by depositing a phagostimulant pheromone that attracts workers. Foraging workers use semiochemicals to communicate with each other,[130] and workers who begin to forage outside of their nest release trail pheromones from their sternal glands. In one species, Nasutitermes costalis, there are three phases in a foraging expedition: first, soldiers scout an area. When they find a food source, they communicate to other soldiers and a small force of workers starts to emerge. In the second phase, workers appear in large numbers at the site. The third phase is marked by a decrease in the number of soldiers present and an increase in the number of workers. Isolated termite workers may engage in Lévy flight behaviour as an optimised strategy for finding their nestmates or foraging for food.

Competition
Competition between two colonies always results in agonistic behaviour towards each other, resulting in fights. These fights can cause mortality on both sides and, in some cases, the gain or loss of territory. "Cemetery pits" may be present, where the bodies of dead termites are buried.

Studies show that when termites encounter each other in foraging areas, some of the termites deliberately block passages to prevent other termites from entering. Dead termites from other colonies found in exploratory tunnels leads to the isolation of the area and thus the need to construct new tunnels. Conflict between two competitors does not always occur. For example, though they might block each other's passages, colonies of Macrotermes bellicosus and Macrotermes subhyalinus are not always aggressive towards each other. Suicide cramming is known in Coptotermes formosanus. Since C. formosanus colonies may get into physical conflict, some termites will tightly squeeze into foraging tunnels and die, successfully blocking the tunnel and ending all agonistic activities.
Among the reproductive caste, neotenic queens may compete with each other to become the dominant queen when there are no primary reproductives. This struggle among the queens leads to the elimination of all but a single queen, which, with the king, will take over the colony.
Ants and termites may compete with each other for nesting space. In particular, ants that prey on termites usually have a negative impact on arboreal nesting species.

Communication
Most termites are blind, so communication primarily occurs through chemical, mechanical and pheromonal cues. These methods of communication are used in a variety of activities, including foraging, locating reproductives, construction of nests, recognition of nestmates, nuptial flight, locating and fighting enemies, and defending the nests. The most common way of communicating is through antennation. A number of pheromones are known, including contact pheromones (which are transmitted when workers are engaged in trophallaxis or grooming) and alarm, trail and sex pheromones. The alarm pheromone and other defensive chemicals are secreted from the frontal gland. Trail pheromones are secreted from the sternal gland, and sex pheromones derive from two glandular sources: the sternal and tergal glands. When termites go out to look for food, they forage in columns along the ground through vegetation. A trail can be identified by the faecal deposits or runways that are covered by objects. Workers leave pheromones on these trails, which are detected by other nestmates through olfactory receptors. Termites can also communicate through mechanical cues, vibrations, and physical contact. These signals are frequently used for alarm communication or for evaluating a food source.

When termites construct their nests, they use predominantly indirect communication. No single termite would be in charge of any particular construction project. Individual termites react rather than think, but at a group level, they exhibit a sort of collective cognition. Specific structures or other objects such as pellets of soil or pillars cause termites to start building. The termite adds these objects onto existing structures, and such behaviour encourages building behaviour in other workers. The result is a self-organised process whereby the information that directs termite activity results from changes in the environment rather than from direct contact among individuals.

Termites can distinguish nestmates and non-nestmates through chemical communication and gut symbionts: chemicals consisting of hydrocarbons released from the cuticle allow the recognition of alien termite species. Each colony has its own distinct odour. This odour is a result of genetic and environmental factors such as the termites' diet and the composition of the bacteria within the termites' intestines.

Defence
Termites rely on alarm communication to defend a colony. Alarm pheromones can be released when the nest has been breached or is being attacked by enemies or potential pathogens. Termites always avoid nestmates infected with Metarhizium anisopliae spores, through vibrational signals released by infected nestmates. Other methods of defence include intense jerking and secretion of fluids from the frontal gland and defecating faeces containing alarm pheromones.

In some species, some soldiers block tunnels to prevent their enemies from entering the nest, and they may deliberately rupture themselves as an act of defence. In cases where the intrusion is coming from a breach that is larger than the soldier's head, defence requires a special formations where soldiers form a phalanx-like formation around the breach and bite at intruders. If an invasion carried out by Megaponera analis is successful, an entire colony may be destroyed, although this scenario is rare.

To termites, any breach of their tunnels or nests is a cause for alarm. When termites detect a potential breach, the soldiers will usually bang their heads apparently to attract other soldiers for defence and to recruit additional workers to repair any breach. Additionally, an alarmed termite will bump into other termites which causes them to be alarmed and to leave pheromone trails to the disturbed area, which is also a way to recruit extra workers.[53]
The pantropical subfamily Nasutitermitinae has a specialised caste of soldiers, known as nasutes, that have the ability to exude noxious liquids through a horn-like frontal projection that they use for defence.Nasutes have lost their mandibles through the course of evolution and must be fed by workers.[56] A wide variety of monoterpene hydrocarbon solvents have been identified in the liquids that nasutes secrete.
Soldiers of the species Globitermes sulphureus 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.[153][154] Another termite, Neocapriterme taracua, also engages in suicidal defence. Workers physically unable to use their mandibles while in a fight form a pouch full of chemicals, then deliberately rupture themselves, releasing toxic chemicals that paralyse and kill their enemies. The soldiers of the neotropical termite family Serritermitidae have a defence strategy which involves front gland autothysis, with the body rupturing between the head and abdomen. When soldiers guarding nest entrances are attacked by intruders, they engage in autothysis, creating a block that denies entry to any attacker.

Workers use several different strategies to deal with their dead, including burying, cannibalism, and avoiding a corpse altogether. To avoid pathogens, termites occasionally engage in necrophoresis, in which a nestmate will carry away a corpse from the colony to dispose of it elsewhere. Which strategy is used depends on the nature of the corpse a worker is dealing with (i.e. the age of the carcass).

Nests
A termite nest can be considered as being composed of two parts, the inanimate and the animate. The animate is all of the termites living inside the colony, and the inanimate part is the structure itself, which is constructed by the termites. Nests can be broadly separated into three main categories: subterranean (completely below ground), epigeal (protruding above the soil surface), and arboreal (built above ground, but always connected to the ground via shelter tubes). Epigeal nests (mounds) protrude from the earth with ground contact and are made out of earth and mud. A nest has many functions such as providing a protected living space and providing shelter against predators. Most termites construct underground colonies rather than multifunctional nests and mounds. Primitive termites of today nest in wooden structures such as logs, stumps and the dead parts of trees, as did termites millions of years ago.

To build their nests, termites primarily use faeces, which have many desirable properties as a construction material. Other building materials include partly digested plant material, used in carton nests (arboreal nests built from faecal elements and wood), and soil, used in subterranean nest and mound construction. Not all nests are visible, as many nests in tropical forests are located underground.[180] Species in the subfamily Apicotermitinae are good examples of subterranean nest builders, as they only dwell inside tunnels. Other termites live in wood, and tunnels are constructed as they feed on the wood. Nests and mounds protect the termites' soft bodies against desiccation, light, pathogens and parasites, as well as providing a fortification against predators. Nests made out of carton are particularly weak, and so the inhabitants use counter-attack strategies against invading predators.

Arboreal carton nests of mangrove swamp-dwelling Nasutitermes are enriched in lignin and depleted in cellulose and xylans. This change is caused by bacterial decay in the gut of the termites: they use their faeces as a carton building material. Arboreal termites nests can account for as much as 2% of above ground carbon storage in Puerto Rican mangrove swamps. These Nasutitermes nests are mainly composed of partially biodegraded wood material from the stems and branches of mangrove trees, namely, Rhizophora mangle (red mangrove), Avicennia germinans (black mangrove) and Laguncularia racemose (white mangrove).

Some species build complex nests called polycalic nests; this habitat is called polycalism. Polycalic species of termites form multiple nests, or calies, connected by subterranean chambers.[100] The termite genera Apicotermes and Trinervitermes are known to have polycalic species. Polycalic nests appear to be less frequent in mound-building species although polycalic arboreal nests have been observed in a few species of Nasutitermes.

Mounds
Nests are considered mounds if they protrude from the earth's surface. A mound provides termites the same protection as a nest but is stronger. Mounds located in areas with torrential and continuous rainfall are at risk of mound erosion due to their clay-rich construction. Those made from carton can provide protection from the rain, and in fact can withstand high precipitation. Certain areas in mounds are used as strong points in case of a breach. For example, Cubitermes colonies build narrow tunnels used as strong points, as the diameter of the tunnels is small enough for soldiers to block.[186] A highly protected chamber, known as the "queens cell", houses the queen and king and is used as a last line of defence.

Species in the genus Macrotermes arguably build the most complex structures in the insect world, constructing enormous mounds. These mounds are among the largest in the world, reaching a height of 8 to 9 metres (26 to 29 feet), and consist of chimneys, pinnacles and ridges. Another termite species, Amitermes meridionalis, can build nests 3 to 4 metres (9 to 13 feet) high and 2.5 metres (8 feet) wide.

The sculptured mounds sometimes have elaborate and distinctive forms, such as those of the compass termite (Amitermes meridionalis and A. laurensis), which builds 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 north-south orientation causes the internal temperature of a mound to increase rapidly during the morning while avoiding overheating from the midday sun. The temperature then remains at a plateau for the rest of the day until the evening.

Shelter tubes
Termites construct shelter tubes, also known as earthen tubes or mud tubes, that start from the ground. These shelter tubes can be found on walls and other structures. Constructed by termites during the night, a time of higher humidity, these tubes provide protection to termites from potential predators, especially ants. Shelter tubes also provide high humidity and darkness and allow workers to collect food sources that cannot be accessed in any other way. These passageways are made from soil and faeces and are normally brown in colour. The size of these shelter tubes depends on the amount of food sources that are available. They range from less than 1 cm to several cm in width, but may extend dozens of metres in length.